Asia's largest bourse has come under heavy criticism since it closed early for the first time ever in January after a scandal at Internet firm Livedoor sparked a flood of selling that threatened to crash its computer system.

The bourse has shortened its afternoon session by 30 minutes since January 19 in the wake of the feared systems overload, which was just the latest in a series of technical problems.

In November the Tokyo Stock Exchange (TSE) suffered its worst-ever system crash which paralyzed the bourse for most of the trading day.

"(The) TSE recognizes that this is a grave situation which could shake the confidence of investors at home and abroad in the financial capital markets of our country," the exchange operator said in a mid-term management plan.

Separately, Japan's number two bourse, the Osaka Securities Exchange, which is independent to the TSE, announced plans to invest 13 billion yen to beef up its computer system.

The TSE's November system failure was the first time in its history of more than half a century that trading in all stocks was halted and its first major system failure since 1997.

The bourse's chief executive, Takuo Tsurushima, quit in December to take the blame for another incident in which a securities firm lost 330 million dollars when the slip of a trader's finger triggered a massive accidental sell order.