Unspecified computer glitches and "connectivity" issues halted trading of all securities on the NYSE on Wednesday, following earlier reports of technical difficulties at the world's largest stock market.

By 3:10 p.m. local time (2110 GMT), nearly four hours later, the exchange was operating normally again, according to a status update on the NYSE's website.

NYSE-listed issues were still trading elsewhere, such as on the Nasdaq OMX Group and BATS Global Markets, the third largest exchange in the US.

"It's under control. We're just waiting for word. There's no sign of panic at all," Reuters quoted Mark Otto of J. Streicher & Co. as saying from the trading floor shortly after the disturbance.

No 'malicious actions'

The midsession trading halt was called at 11:32 a.m. local time (1532 GMT), just hours after technicians said they had resolved an issue that had led some customers to not receive acknowledgements on orders submitted on some stock symbols. Traders were encouraged to cancel any unconfirmed orders.

Even before the freeze, US markets were down over concern about protracted losses in China. The S&P 500 hit a session low and the Dow Jones industrial average and Nasdaq had both sloughed off more than 1 percent.

Confirming an earlier statement from the NYSE, the White House said there was no indication of "malicious actions" in the shutdown. A government spokesman added that US President Barack Obama had been briefed on the trading halt by senior white house officials, including his homeland security adviser, Lisa Monaco.

The Deparment of Homeland Security said it was "still investigating" the incident, but added that it had no reasons to believe that the disruption was the result of a cyber attack.

cjc/pad (Reuters, dpa, AFP)