A killer whale has reportedly been spotted off the coast of Norfolk.

The sighting has been described as “highly reliable” by county mammal recorder Dr David Leech, the BBC reported.

The Orca was spotted breach the water off Sheringham near Cromer by birdwatchers Giles Dunmore and Phil Vines.

The pair were watching seabirds with a telescope when they made their discovery.

It is believed to be the first time a killer whale has been spotted off Norfolk since records began in the early 1900s, the Telegraph said.

Mr Dunmore said: "I can't estimate how far out it was but I suddenly saw an area of disturbed water and then this black hump came out of the sea and a great big, black dorsal fin - then it disappeared. It was heading eastwards.

"I yelled out and Phil was desperately trying to see it. A few seconds later he yelled out too, with a fine Anglo-Saxon expletive."

Dr Leech said: “With the experience of the observer and knowing that they had good optical kit, because they were using telescopes to watch the birds, I think in combination that sounds like a really quite a reliable source."

It’s thought the whale may have been drawn off course by food sources such as seals and other marine life.

The information is being referred to the Sea Watch Foundation and Marine Conservation Society.