A Japanese woman was raped on Friday on the island of Okinawa - reluctant host to most US forces in Japan - and police are questioning several US servicemen and seeking a man who fled the scene.
The attack occurred just hours before the Japanese Prime Minister, Mr Junichiro Koizumi, left for the United States for a summit with President Bush. The US military presence on Okinawa is certain to be on the agenda.
"There is no doubt that she was raped," an official of the Okinawa police said. Police are questioning at least four US servicemen as well as several civilian foreigners and Japanese who were in the carpark of the American Village shopping district in Chatan, where the rape took place at about 2 a.m. on Thursday. The woman, in her 20s, told investigators she was raped by a black foreigner. The man fled in a vehicle with US military licence plates, Kyodo news agency said.
"We are looking for the man," a police spokesman said, adding "We also suspect that there may be others who co-operated."
Chatan, a town in central Okinawa some 1,600 km south of Tokyo, is filled with bars catering to troops from nearby military bases, including Kadena Air Force Base, the largest US air base in Asia.
"I have heard that such an incident occurred but have not heard the details," Mr Koizumi told a news conference.
"After hearing the facts, we should act if we must. But regarding such crimes, both sides have to take measures to ensure that these don't happen," he said.
Should the rape turn out to involve US servicemen, it could overshadow his summit with President Bush and fuel anger on Okinawa, where anti-US forces sentiment has festered for years, in large part due to crimes committed by the military.
"We are aware of an alleged incident in Okinawa. US bases there are co-operating fully with the Okinawa prefecture of police in their investigation," Pentagon spokesman Lieutenant Commander Jeff Davis said in Washington.
Mr Koji Omi, state minister in charge of Okinawa issues, responded swiftly. "We don't know the details but if it is true, it is extremely regrettable," he told a news conference in Tokyo.
"We must issue a stern protest (to the US military) and take necessary action," he said.
About 26,000 of the 48,000 US servicemen and women in Japan are stationed on Okinawa, or just over one-quarter of the total US military presence in the Asia-Pacific region. The bases would play an important role in the missile defence system planned by the two countries.
The US military presence has been in dispute ever since local resentment erupted into widespread protests in 1995 after the abduction and rape of a 12-yearold girl by three US servicemen.
That incident put into sharp focus questions about the status of Japan-US security ties in a post-Cold War world - questions that culminated in calls this year from Okinawa governor Mr Keiichi Inamine for a reduction in the US forces.
A recent spate of crimes in which military personnel have been implicated has further inflamed the anti-base feelings on Okinawa.
Mr Koizumi promised last week to do whatever he could to solve the problems faced by Okinawa residents, telling a gathering at a war memorial on the southern island that he would strive to reduce their burden.
Foreign Minister Makiko Tanaka raised the issue of moving some US military training out of Okinawa when she met US Secretary of State Colin Powell in Washington two weeks ago.