The London FTSE 100 index failed to open at the start of European trading on Friday.
The London Stock Exchange (LSE) is investigating a potential problem with trading services, according to an official statement.
Futures indicated a higher opening for FTSE on Friday.
"One of those things that is not so uncommon, the first of June 2018 for the FTSE100; if there is a sharp movement elsewhere, it may trigger a strange spike stroke when opened, but this is just a function to balance the imbalances. " Mark Ostwald, global strategist and chief economist at ADM Investor Services International, told CNBC by email on Friday.
The FTSE 100, the UK's blue chip index, reached a six-month low on Thursday as the escalating trade war between the United States and China and growing concern for the global economy saw global equities go on sale.
The index has fallen by more than 6.7 percent over a 30-day period, but is still above 5 percent since the beginning of the year.
The Financial Times Stock Exchange 100 Index, or the FTSE 100 Index, includes the 100 LSE-listed companies with the highest market cap. The total market capacity of the FTSE 100 index is 1.89 trillion pounds ($ 2.28 trillion) – more than twice the capacity of Apple.
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