Japanese police arrested an American sailor Saturday on charges of robbing and beating a Japanese woman to death — a case likely to further stoke opposition to U.S. military presence in Japan.

William Oliver Reese, 21, was arrested after being transferred to police from the U.S. Navy base in Yokosuka, about 30 miles southwest of Tokyo, said police officials in Yokosuka and Kanagawa prefecture, both speaking on condition of anonymity citing police protocol.

The U.S. military previously agreed to hand over Reese, who police said admitted during questioning that he killed Yoshie Sato, 56, in Yokosuka on Tuesday. She was found beaten and unconscious that day and later died of internal bleeding.

Reese, who also has been identified in Japanese media, is accused of robbing Sato of $129.

The U.S. Navy in Japan said it would continue cooperating with Japanese authorities in the case.

"The U.S. Navy's responsibility to see this matter through to its rightful conclusion does not end here, and we will continue to provide our complete support and cooperation with Japanese authorities," said Rear Adm. James Kelly, the commander of U.S. naval forces in Japan.

Reese was based on the aircraft carrier USS Kitty Hawk and has been in Japan since May 2004. He has been in the Navy for about two years and Japan was his first assignment, according to the Navy.

The case risks further inflaming local opposition to plans to build an American military airstrip in the southern island of Okinawa and base a U.S. nuclear-powered warship at Yokosuka for the first time.

Reflecting the sensitivity of the case, the U.S. Embassy issued a statement Friday expressing regret for the crime.

"The U.S. military and the American people are deeply shocked and saddened by this event," U.S. Ambassador Thomas Schieffer said.

In 1995, an uproar over the rape of a 12-year-old girl by three U.S. servicemen on Okinawa triggered massive protests and led to the relocation of an air base to a less densely populated part of the island.

The rape case also resulted in an agreement with the U.S. military that it would hand over American suspects in serious crimes to Japanese authorities for pre-indictment investigation.

About 50,000 U.S. troops are stationed in Japan under a joint security pact, but Tokyo and Washington agreed in October to move 7,000 Marines from Okinawa to the U.S. territory of Guam and shift some of the remaining troops within Japan.