Protesters from Greenpeace are attempting to scale The Shard in London.

The six women started to climb the outside of Europe's tallest building in the early hours of Thursday and are attempting to install "a work of art" at the top.

Shortly before lunchtime, the group reached the building's halfway point, making it to around 180 metres by early afternoon, higher than the Pyramids and Big Ben.

Earlier, the campaign group confirmed it was behind the stunt on its official Twitter feed.

And it posted a photo of the climbers:

A Met Police spokesman told The Huffington Post UK officers had been called to the scene at 4.20am.

Six protesters were currently going up the buliding, he said, with Met and British Transport Police officers at the scene.

They are thought to have climbed to the top of London Bridge station to access the 72-storey skyscraper.

Greenpeace said it had chosen The Shard because it towered over the London offices of Shell, which it said was leading controversial drilling in the Arctic.

It said: "The Greenpeace volunteers began their climb at 4am this morning, and if they succeed – which is far from certain – they expect the gruelling project to take most of the day.

"The lead climbers are ‘free climbing’ (scaling the building without assistance) but are fixing safety ropes as they progress.

shard

Greenpeace protesters climbs up The Shard, the tallest building in western Europe.

"They are carrying the huge work of art in backpacks and will install it this afternoon if they reach the summit."

One of the climbers, 27-year-old Swede Sandra Lamborn, said an oil spill in the Arctic would be "devastating".

She claimed drilling was only possible because climate change was melting the ice cap.

"That’s why I’m climbing that skyscraper slap bang in the middle of Shell’s three main offices, because they want to drill for the fuels that caused the melting in the first place," she said.

"It’s crazy. I’ve come to London to make a stand. We’re drawing a line in the ice and saying to the oil companies, you come no further.”

A Shell spokesman said: “We respect the right of individuals and organisations to engage in a free and frank exchange of views about our operations.

"Recognising the right of individuals to express their point of view, we only ask that they do so with their safety and the safety of others, including Shell personnel and customers in mind.”

He added: "Shell has been operating in the Arctic and sub-Arctic since the early 20th century, giving us the technical experience and know-how to explore for and produce oil and gas responsibly."

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  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: A protester from the environmental charity Greenpeace is watched by workers as she attempts to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: Protesters from the environmental charity Greenpeace attempt to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: Protesters from the environmental charity Greenpeace are watched by workers as they attempt to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: A protester from the environmental charity Greenpeace is watched by workers as she attempts to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: A protester from the environmental charity Greenpeace is watched by workers as she attempts to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: Protesters from the environmental charity Greenpeace attempt to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • Greenpeace Protesters Climb Up The Shard

    LONDON, ENGLAND - JULY 11: Protesters from the environmental charity Greenpeace attempt to scale the tallest building in western Europe, The Shard, in a bid to unveil a giant banner from the top on July 11, 2013 in London, England. The six female protesters began their unauthorised ascent of the 310 metre high skyscraper shortly after 4am with the intention of highlighting the environmental damage caused by drilling for oil in the Arctic by Shell. (Photo by Oli Scarff/Getty Images)

  • People watch Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Reflected in a nearby building, Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Reflected in a nearby building, Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Greenpeace protest at the Shard

    Greenpeace activists, part of a group of six women, as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Greenpeace protest at the Shard

    A Greenpeace activist, part of a group of six women, as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Greenpeace protest at the Shard

    Onlooker watch a group of six women Greenpeace activists as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Greenpeace protest at the Shard

    Onlooker watch a group of six women Greenpeace activists as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Greenpeace protest at the Shard

    Greenpeace activists, part of a group of six women, as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Greenpeace protest at the Shard

    Greenpeace activists, part of a group of six women, as they climb the Shard in central London, in protest at drilling in the Arctic.

  • six Greenpeace protesters climbs up The Shard,

    Ali (blue helmet) hangs on while Sandra (black helmet) does... what is she doing? #iceclimb

  • One of six Greenpeace protesters climbs up The Shard, the tallest building in western Europe, as workers look from a window, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Greenpeace protesters climbs up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • A man takes a photo from the inside as a Greenpeace protester climbs up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Greenpeace protesters climbs up The Shard, the tallest building in western Europe, as a plane is reflected on the building during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • @GreenpeaceUK: Sabine & @victohenry clinging on as they attempt #iceclimb

  • Go Liesbeth! #iceclimb Credit: Greenpeace

  • Liam Jacquin

  • BO4GDIGCUAALaC

  • Six women climbers start their ascent of the Shard, London's tallest building, for Greenpeace's Save the Arctic campaign.

  • 993616_10151292389974229_1086346340_n

  • credit: Greenpeace

  • Greenpeace activists begin to climb the Shard

  • London Aerial Views - Stock

    An aerial view of The Thames in London showing The Shard building, Tower Bridge and Canary Wharf in the distance.

  • London Aerial Views - Stock

    An aerial view of central London including The Shard building and The City (right).

  • London Aerial Views - Stock

    An aerial view of The Thames in London showing The Shard building (right) and The City (left). The Olympic Stadium is also visible at the top.

  • City Views - London

    General view of the Shard building, London

  • London Aerial Views - Stock

    An aerial view of The Thames in London showing The Shard building, Tower Bridge and Canary Wharf in the distance.

  • Greenpeace protest at the Shard

    Onlooker watch a group of six women Greenpeace activists as they climb the Shard in central London, in protest at drilling in the Arctic.

  • Reflected in a nearby building, Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • People watch Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • People watch Greenpeace protesters climb up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Greenpeace protesters climbs up The Shard, the tallest building in western Europe, as a plane is reflected on the building during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • A man takes a photo from the inside as a Greenpeace protester climbs up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • One of six Greenpeace protesters climbs up The Shard, the tallest building in western Europe, as workers look from a window, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)

  • Greenpeace protesters climbs up The Shard, the tallest building in western Europe, during a protest against the oil company Shell's drilling in the Arctic, Thursday, July 11, 2013. (AP Photo/Sang Tan)