The employees of unlisted Fujita were detained in northern China’s Hebei province last month while Beijing and Tokyo were embroiled in a territorial row sparked by Japan’s detention of a Chinese fishing boat captain in disputed seas.

They were in China for a project to dispose of chemical weapons abandoned there by the Japanese military at the end of World War Two.

China on Sept. 30 released the three others, after they acknowledged “having violated Chinese law and showed regret for their mistake,” state-run Xinhua said at the time.

The fourth, named as Sadamu Takahashi, was released on bail, according to authorities in Hebei’s provincial capital of Shijiazhuang, cited by the brief Xinhua report.

He was instructed “to write a statement of repentance” and has already “left the place where he was residing under surveillance after going through legal procedures,” Xinhua added.

The report said the four had been detained “for intruding (into) the Chinese military zone and illegal filming OF military targets.” It gave no further details.

Indications of improving ties followed talks between the Chinese and Japanese prime ministers on the sidelines of a summit in Belgium this week. Both called for better relations, while stressing their respective claims to the islands.

On Saturday, Japanese Prime Minister Naota Kan said he was pleased that ties with Beijing were back on track.

“I’m relieved,” Kan told reporters in remarks broadcast on NHK public TV. “In my conversation with (Chinese) Premier Wen Jiabao, we agreed to resume high-level political exchanges and this has begun. So various things are returning to the way they were.”

Kyodo news agency quoted the Japanese embassy in China as saying that Takahashi was in “good condition” and could be back in Japan as early as Sunday.

China and Japan, Asia’s two largest economies, have acted to ease tension following the stand-off over uninhabited islets in the East China Sea, called Diaoyu in China and Senkaku in Japan.

On Saturday, four Japanese lawmakers inspected the islands from the air, Japanese media reported.

The spats have underscored the fragility of a relationship long troubled by bitter Chinese attitudes toward Japan’s wartime occupation as well as by present-day mistrust as China edges past Japan as the world’s second biggest economy.

China canceled diplomatic meetings and student visits in protest against the trawler captain’s detention, and industry sources cited concerns that Beijing appeared to hold back shipments of rare earth minerals vital for electronics and auto parts.