The disruption began at about 11:30am local time, but did not appear to affect other stock markets.

The NYSE said in tweets: "The issue we are experiencing is an internal technical issue and is not the result of a cyber breach.

"We chose to suspend trading on NYSE to avoid problems arising from our technical issue.

"NYSE-listed securities continue to trade unaffected on other market centers."

It said all open orders would be cancelled.

The Nasdaq exchange, also based in New York, said in a tweet that its systems were operating normally.

The Nasdaq halted trades for three hours in August 2013 due to technical problems.

The NYSE is the world's largest equity exchange with a market capitalisation of about $20trn.

The White House said it was monitoring the situation, along with the Treasury Department.

The Securities and Exchange Commission, the US financial markets regulator, said it was also keeping an eye on the NYSE halt.

Earlier on Wednesday, United Airlines grounded all US flights temporarily because of a computer glitch.

The Department of Homeland Security said it was investigating, but had so far found no sign of malicious activity in either incident.

The Wall Street Journal meanwhile said its website was suffering "technical difficulties".

But it was unclear if that issue was caused by a surge in readers looking for information about the NYSE breakdown.