Twitter Inc gained 4.2pc after it reported quarterly revenue growth, while Snapchat-owner Snap Inc surged 22.5pc on beating estimates for user growth and revenue.
All three major U.S. stock indexes ended the session sharply lower, with the S&P and the Nasdaq suffering their largest one-day percentage drop since mid-May.
London investors brushed off the expected announcement Monday from the UK government that it will delay the lifting of its remaining lockdown restrictions.