London's blue chip share index has tumbled deeper into the red amid a global stock market rout sparked off by woes in China and plunging oil prices.
The FTSE 100 Index slumped below the 6000 mark after diving by more than 140 points - a fall of 2.4% - in the wake of more heavy losses in Asia.
China's benchmark Shanghai Composite Index plunged more than 7% overnight - triggering the second so-called circuit breaker move to halt trading this week.
Markets in Asia are being hit by the withdrawal of Chinese government measures introduced last year to prop up share prices, while investors are also unnerved by signs of a worsening slowdown in China's economy.
Steep falls in oil prices are compounding the worldwide stock market sell-off, with the cost of benchmark Brent crude collapsing to fresh 11-year lows, sinking below 33 US dollars a barrel.
The picture was dire across Europe, with the Dax in Germany shedding more than 3% and France's Cac 40 off 2.5%.
Connor Campbell, financial analyst at Spreadex, said: "The global indices have been left in the midst of what is arguably their most calamitous week since the storied trading of last August."