Japan's Tokyo Stock Exchange has suspended trading in all shares due to technical problems, the exchange said on Thursday, adding it does not know when the issue will be resolved.

Bourses in Nagoya, Fukuoka and Sapporo, which use the TSE's system, also suspended trading. Trading in the derivative-focused Osaka Exchange is not affected.

Tokyo's roughly $6 trillion market is the world's third largest, after New York and Shanghai, according to data from the World Federation of Exchanges.

A statement from the TSE gave no further details.

The trading halt is certain to frustrate investors who are jockeying for position after the first US presidential debate, and any prolonged problems could potentially cast doubts on quality of the TSE's infrastructure.

“Stocks were expected to rebound quite strongly today after the presidential debate, so this system problem has poured cold water over that,” said Norihiro Fujito, chief investment strategist at Mitsubishi UFJ Morgan Stanley Securities.

“We still don't know the cause, and I don't think it's a big problem. But it does highlight the importance of going digital.”

Nikkei futures, which trade in Osaka, rose 0.35% on Thursday, in line with a rise in US stocks overnight.

The Nikkei fell 1.5% on Wednesday, its biggest decline in two months, as an acrimonious debate between US President Donald Trump and Democrat Joe Biden highlighted the risk of an inconclusive outcome to the presidential election in November.

The TSE had been prone to system troubles in the past and was notorious for sluggish trading, but problems have been relatively rare since it expanded its capability with the introduction of a new system in 2010.

The TSE had suspended trading in October 2018 due to problems with its trading system.

In 2006, news of an accounting scandal at the then popular internet firm Livedoor Co sparked a massive sell-off. Unable to handle, the rush of orders from panicked investors, the Tokyo exchange had to curtail trading hours for three months.