TOKYO (Reuters) - Police in Japan are investigating allegations that four U.S. Marines raped a 19-year-old Japanese woman, media and officials said, the latest episode to plague the U.S. military’s relations with local communities.

U.S. Marines' F-18 fighters prepare for takeoff at U.S. Marine Corps Air Station in Iwakuni, western Japan in this March 2, 2006 file photo. Police in Japan are investigating allegations that four U.S. Marines raped a 19-year-old Japanese woman, media and officials said, the latest episode to plague the U.S. military's relations with local communities. REUTERS/Toru Hanai/Files

“I have received a report of a Japanese woman being raped by several men in the early morning of October 14 in the city of Hiroshima,” Chief Cabinet Secretary Nobutaka Machimura told a news conference on Friday.

“The Hiroshima police are proceeding with the investigation in cooperation with U.S. forces in Japan,” he said. “Of course, if it is true it is unforgivable.”

Public broadcaster NHK reported that four U.S. Marines from Iwakuni Marine Corps Air Station in southwest Japan had raped a 19-year-old woman in a car at a car park in nearby Hiroshima City after meeting her at an event hall.

The mayor of Iwakuni had suggested this week he was willing to discuss the expansion of the Marine base.

Major G.A. Canedo, public affairs officer at the base, said four Marines had been confined there.

“We are aware of the allegations. The matter is being investigated and we are cooperating fully with local authorities,” Canedo said, but declined to give further details.

Police in Hiroshima confirmed that an investigation was under way but declined to say whether they would demand that the four Marines be handed over into their custody.

A U.S.-Japan pact governing the conduct of U.S. military personnel in Japan does not require the transfer of military suspects until they are charged, but Washington has agreed to favorably consider pre-indictment transfers in cases of suspected rape, murder and other heinous crimes.

Japan is host to about 50,000 U.S. military personnel as part of the U.S.-Japan security alliance, but friction often occurs with local communities near the bases because of concern about crime, accidents and noise.

The 1995 rape of a Japanese schoolgirl by three U.S. servicemen on the southern island of Okinawa sparked huge protests.

Last year voters in Iwakuni rejected in a non-binding referendum a plan to expand the nearby Marine base by moving carrier-based planes and personnel from Atsugi naval base near Tokyo.