The US Nasdaq index has closed above its dotcom boom record for the first time in 15 years.
The FTSE 100 has fallen 1.3% as geopolitical tensions and yesterday's tech sell-off put fresh pressure on UK stocks.
US stock markets followed in the footsteps of the FTSE 100 on Monday, with the Nasdaq reaching its highest level for almost 15 years.
Goldman Sachs has sought to reassure clients spooked by the recent falls in tech stocks, saying the US is unlikely to suffer a 2000-style crash.
US equity fund managers have begun cutting their exposure to technology stocks as the highly-rated sector falls out of favour with some investors following a long winning streak.
The FTSE 100 was down over 1% by 11am, with Hargreaves Lansdown leading the market lower after being downgraded by Morgan Stanley.
Facebook's share price fell as much as 5% in after-hours trading as the company announced a deal to buy chat application WhatsApp for some $19bn.