The FTSE 100 nosedived more than 6% in opening trades as markets continue to react to last week's shock tariff announcement from US President Donald Trump.
About 40 minutes into trade, London's blue-chip index had retraced some of its losses and was down 373 points, or about 4.6%, at 7,680.
Glencore is leading the fallers this morning, down 12.4%, Rolls-Royce Group is down 12.1% and Babcock International is 10.6% lower.
Shell has put out an update on its first quarter 2025 outlook ahead of the full quarterly results announcement scheduled for 2 May.
Production for the Integrated Gas division is expected to be slightly higher than last year, while oil production is projected at 1.79-1.89 million barrels of oil equivalent per day, versus 1,859 million last time. With oil prices also tumbling, its shares are also under pressure this morning.
Other global markets are also under pressure, with Hong Kong's Hang Seng down 12.5%, the Shanghai composite losing close to 9% and Japan's Nikkei down almost 7%.
Futures markets are also pointing to more losses for US stocks today.