The trouble, a problem with a server for the data distribution system, meant there was no morning trade in Sony one day after it announced a new chief executive and ahead of the release of quarterly results later in the day.

Hiroaki Uji, director of IT development at the Tokyo Stock Exchange, told a news conference that the exchange was still investigating the problem but ruled out the possibility of cyber terrorism when asked by reporters.

The glitch affected 153 Topix shares, some exchange-traded funds (ETFs), real estate investment trusts (REITs) and convertible bonds.

"This is absolutely ridiculous. Absolutely ridiculous. On a day like today, it's earnings season for god's sake," a trader said.

The issue was resolved by the start of the afternoon session at 12:30 p.m. (10:30 p.m. ET).

The Nikkei average .N225 ended 0.8 percent higher at 8,876.82 but trading volume did not appear to suffer too much. Volume hit its highest level since January 20, with 2.25 billion shares changing hands on the main board.

"It's difficult to understand broader market moves without seeing some of these major blue chips (in the morning session), although the Nikkei gains seem in line with futures prices," said Toshiyuki Kanayama, senior market analyst at Monex Inc.

The market did not markedly shift on the resumption, and an hour into the session the Nikkei was up 0.9 percent.

Traders said it was the most extensive trouble for Tokyo cash shares since November 1, 2005, when trading in 2,520 instruments were suspended due to system problems.

"The TSE has damaged confidence as it has caused trouble at the peak of earning season," said a trader at a Japanese brokerage.

(Reporting by Hideyuki Sano and Mari Saito; Editing by John Mair and Chris Gallagher)

• A Permanent Economic Emergency