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.

NYSE-listed issues were still trading on other exchanges, according to a status page on the NYSE's website.

"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.

The mid-session 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.

cjc/pad (Reuters, dpa)