Tokyo stocks surged Wednesday morning, with the key Nikkei index temporarily rising more than 6 percent and erasing about half of the previous day's losses triggered by deepening troubles at a quake-hit nuclear power plant.

The 225-issue Nikkei Stock Average rose to 9,168.51 at one point before ending the morning session at 8,981.14, up 375.99 points, or 4.37 percent, from Tuesday.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange was up 39.17 points, or 5.11 percent, to 805.90.

Nearly all 33 sectors on the TSE rose, with the rubber products sector leading gainers, followed by the mining and real estate sectors. The electric and gas sector extended losses, becoming the only decliner.

The Nikkei index rebounded after tumbling more than 1,600 points over the last two days and hitting the lowest closing since April 28, 2009 on Tuesday.

But the market slightly lost momentum toward the morning closing as investors continued to keep their eyes on the crisis at Tokyo Electric Power Co.'s Fukushima No. 1 plant as another fire broke out at one of its reactors on Wednesday, brokers said.

Yumi Nishimura, senior market analyst at Daiwa Securities Capital Markets Co., said she believes the upsurge is based on an assumption that crisis levels at the nuclear plant will not worsen significantly from now on.

The market is likely to be weighed down also by investor concern about the economic outlook of the world's third largest economy after the devastating earthquake, brokers said.