BEIJING — China is investigating four Japanese suspected of illegally filming military targets and entering a military zone without authorization, state media reported amid a tense diplomatic spat between Beijing and Tokyo over a fishing boat collision near disputed islands.
China's state-run Xinhua News Agency cited state security authorities in the northern city of Shijiazhuang as saying they had "taken measures" against the four Japanese "after receiving a report about their illegal activities." There was no elaboration.
The authorities accuse the Japanese of entering a military zone without authorization in Hebei province, the capital of which is Shijiazhuang.
The brief report late Thursday night did not say whether the four Japanese are in detention.
The four men are believed to be employees of Fujita Corp., a Tokyo-based construction and urban redevelopment company.
"We are pretty certain they are our employees," said Fujita spokesman Yoshiaki Onodera. "But we have not spoken with them, so we don't know how they came to be questioned."
Onodera said he could not confirm Japanese media reports saying that the men were preparing a bid on a project to dispose of abandoned chemical weapons from World War II.
The Japanese Foreign Ministry confirmed that it had received word from the Chinese government Thursday night about the incident. It did not have further details, including whether the men had been arrested or merely questioned.
The news could further sour relations that have deteriorated badly since earlier this month when Japan arrested a Chinese captain whose fishing boat collided with Japanese coast guard vessels near a string of islands in the East China Sea. Called Diaoyu or Diaoyutai in Chinese and Senkaku in Japanese, the islands are controlled by Japan, but are also claimed by China. They are surrounded by rich fishing grounds and are regularly occupied by nationalists from both sides.
Japan extended the detention of the Chinese captain Sunday, and Beijing reacted quickly, suspending high-level contacts with Tokyo and ruling out a meeting between Premier Wen Jiabao and Japanese Prime Minister Naoto Kan during U.N. meetings in New York this week.
On Tuesday, Wen threatened "further action" against Japan if it did not release the Chinese captain immediately.
Meanwhile, the United States on Thursday urged the two powers to quickly resolve the dispute and a military official said that Washington was committed to strongly supporting Japan, one of America's closest allies in the Pacific.
At a Pentagon news conference, Chairman of the Joint Chiefs of Staff Adm. Mike Mullen said the U.S. was tracking the situation closely and hoped that diplomatic efforts would ease tensions soon.
"And obviously we're very, very strongly in support of ... our ally in that region, Japan," Mullen told reporters.
Defense Secretary Robert Gates added "and we would fulfill our alliance responsibilities," without offering more specifics.
But besides hoping that tensions ease between China and Japan, Mullen said "we haven't seen anything that would, I guess, raise the alarm levels higher than that."
The dispute faces a test on Sept. 29, the deadline by which Japanese prosecutors must decide whether to charge the Chinese captain. Fourteen crew members and the boat have been returned.
Associated Press writer Tomoko A. Hosaka in Tokyo contributed to this report.