A 20-year-old United States Marine has been arrested in Japan's Okinawa prefecture on suspicion of murdering and robbing a Japanese woman, police said on Sunday.

Devin Jacob Ballard, a lance corporal assigned to the III Marine Expeditionary Force and based at Marine Corps Air Station Futenma, is suspected of killing Anna Yagi, 39, in a hotel room in Naha, the prefectural capital, on Saturday. Police allege he also took her wallet and backpack. Ballard has denied the allegations, according to police.

The body of Yagi was discovered in the early hours of Saturday. The arrest was made a day later.

Japanese Prime Minister Sanae Takaichi condemned what she called an "extremely brutal and heinous incident" and said Japan had lodged a strong protest with the United States. She demanded maximum cooperation with the investigation, strict discipline among US military personnel and thorough measures to prevent a recurrence.

The US Embassy in Tokyo said it was aware a service member was in custody and extended condolences to the victim's family. The III Marine Expeditionary Force said it was actively cooperating with Japanese authorities and that the Marine remained in local custody.

Most of the roughly 18,000 Japan-based US Marines are stationed in Okinawa, a presence that has long stirred local resentment over noise, aircraft accidents and the conduct of personnel. The 1995 rape of a 12-year-old Okinawan girl by three servicemen sparked mass protests. The latest case could complicate efforts to relocate Marines from the busy Futenma base to a more remote facility at Henoko.