A US marine has been arrested in the Okinawa island chain after he was accused of robbing and murdering a Japanese woman.

Japan’s prime minister has condemned the incident and her country has registered “strong protests” with the US, which has a large military presence across Okinawa prefecture.

Lance corporal Devin Jacob Ballard, 20, is suspected of killing Anna Yagi, 39, in a hotel in the prefecture’s capital Naha and taking her wallet and backpack, local police said.

Mr Ballard has denied the allegations.

“The occurrence of such an ​extremely brutal and vicious incident is extremely regrettable,” prime minister Sanae Takaichi said in a statement.

“The government of Japan strongly protests to the US side and strongly seeks ​maximum cooperation with the investigation,” she said.

Japan has sought the tightening of discipline of US troops stationed in the country and thorough ​measures to prevent a recurrence.

The suspect, based at Marine Corps Air Station Futenma, is in Japanese custody, and the US embassy and Marine Corps said they were cooperating with the local ​authorities.

A local police officer reportedly questioned and detained the marine when he was walking alone on a street in Naha’s entertainment district.

Police are treating the incident as a robbery-murder, according to local news reports.

“The Marine Corps takes these allegations very seriously and expects every Marine to adhere to the highest standards of behaviour,” it said.

“Such an incident is unacceptable, and I am deeply outraged,” Japanese defence minister Shinjiro Koizumi said.

US ambassador to Japan, George Glass, posted on X that he offered “sincere condolences” and pledged “full cooperation as the investigation continues”.

“We extend our sincere condolences to the victim’s family,” the US embassy in Tokyo wrote on X.

Most of America’s Japan-based marines are stationed in Okinawa, which ​includes the island of Yonaguni about 100km (60 miles) from Taiwan. The region is viewed by Tokyo and Washington as key ​in deterring potential aggression from China.

Locals in Okinawa have repeatedly shown resentment over issues such as noise, aircraft ​crashes, and the conduct of US personnel.

Particularly, crimes involving US military personnel stationed in Japan, including murder, rape, and robbery, have long been a source of public concern.

In Okinawa, local police handled over 100 criminal cases involving US personnel in 2025 alone, according to an official from the prefecture.

The rape of a ​12-year-old Okinawan ⁠girl by three US servicemen in 1995 sparked widespread protests.

Saturday’s murder-robbery could complicate the Japanese prime minister’s efforts to move some US marines from the busy Futenma air base in Okinawa to a more remote facility at Henoko.