Trading in Barclays and RBS shares was suspended on Monday morning following heavy losses on the London Stock Exchange.
Barclays share price fell by 10.3 per cent and RBS fell 15 per cent on Monday morning, triggering automatic circuit breakers that kick in when a share price falls more than 8 per cent.
When that happens, automatic continuous trading is temporarily suspended and the affected shares are placed into an auction to recalculate the value of the stock.
This allows the market to decide on an appropriate value for the stock before automatic trading resumes.
Barclays and RBS shares were offline for about five minutes, a spokesperson for the London Stock Exchange said.
Bank shares have been hard hit following the UK's decision to leave the EU on Friday.
Barclays was trading at 127.20, down 17.35 per cent, while RBS was trading at 173.79p, down 15.35 per cent, by the time the stock exchange closed on Monday.
Lloyds was down 10.26 per cent at 51.15p, after falling more than 20 per cent on Monday.
RBS shares have lost £10 billion in their market value since Thursday, or more than the net contribution of the UK to the EU in 2015, which was estimated to be about £8.5 billion. The net contribution is the difference between what the UK paid to the EU and what it got back in spending in the UK.
Bank bosses have sought to reassure investors after the UK voted to leave the EU in a referendum on June 23.
In a statement, Douglas Flint, HSBC group chairman, said that the bank's commitment to British businesses remains undiminished.
“We are today entering a new era for Britain and British business. The work to establish fresh terms of trade with our European and global partners will be complex and time consuming. We will be working tirelessly in the coming weeks and months to help our customers adjust to and prepare for the new environment,” Flint said.
Jes Staley, chief executive of Barclays, said in a statement that the bank was ready to do “whatever it takes” to serve its clients.
“We are a transatlantic consumer, corporate and investment bank, anchored in the UK and the US. That remains the core of our strength and the Barclays of the future,” he said.
The Bank of England said it was ”monitoring developments closely“ and would take ”all necessary steps“ to support monetary stability.
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