Two U.S. Navy sailors have been arrested in Okinawa for the alleged rape of a local woman. The arrests come at a rocky time for the U.S. military presence on Okinawa, which is home to half the 50,000 American military forces based in Japan.

Seaman Christopher Browning and Petty Officer 3rd Class Skyler Dozierwalker were arrested early Wednesday by Okinawan authorities after a local woman alleged that she had been sexually assaulted and robbed in front of her apartment building.

A Navy official says that at approximately 4 a.m. Tuesday a group of sailors allegedly followed a 27-year-old woman to her residence.

Three sailors were picked up at 6 a.m. after she made a report to Okinawan authorities, but only Browning and Dozierwalker remain in custody.

The Japanese Foreign Ministry lodged a formal protest over the incident with the U.S. embassy in Japan. Speaking to how seriously the incident is being taken by American diplomats in Japan, the embassy released a statement from U.S. Ambassador John Roos at 1:28 a.m. local time, saying the U.S. government is "extremely concerned" by the allegations.

"We are committed to cooperating fully with the Japanese authorities in their investigation," he continued. " I am also in close contact with the Commander, U.S. Forces Japan. These allegations, given their seriousness, will continue to command my full personal attention."

The Pentagon also released a statement on the incident saying "The Defense Department takes all allegations involving misconduct by service members seriously wherever they may occur." It added, that "The U.S. Navy in Japan is focused on cooperating and supporting the Okinawa Police investigation."

The Okinawa governor, Hirokazu Nakaima, is expected to fly to Tokyo today, to lodge a formal complaint with the U.S. embassy in person.

For decades there has been significant local opposition to the continued presence of large American military bases on the island, particularly the Marine base in Futenma. The most recent flare-up involved the Marine deployment to the island of tilt rotor Osprey aircraft. Local government officials said the aircraft posed a safety risk following two recent Osprey crashes that recalled the aircraft's shaky safety record very early in its development.

There were massive protests on the island in 1995 following the rape of a 12-year-old schoolgirl by three U.S. Marines.

Per the Status of Forces Agreement between the U.S. and Japan, Japanese authorities are holding the sailors and have primary jurisdiction because it involved a Japanese national. The Navy's Criminal Investigative Service is also conducting its own investigation and providing support to Okinawan authorities.

The Navy official says the sailors are based at Fort Worth Naval Air Base in Texas and were temporarily deployed to Japan as part of the crew of a Navy cargo plane.

The plane's crew had flown a mission from Atsugi in Japan to Okinawa, but was required to stay the night on the island because of crew rest requirements.

The alleged incident is said to have occurred during their stay.