Japanese Prime Minister Sanae Takaichi registered a protest with the United States on Sunday after a US Marine was ​arrested on suspicion of robbing and murdering a Japanese woman in ‌Okinawa.

Lance Corporal Devin Jacob Ballard, 20, is suspected of killing Anna Yagi, 39, in a hotel in Naha, the capital of the southernmost prefecture, on Saturday and taking her wallet and backpack, ​police said. Ballard denied the allegations, police said.

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

“The government of Japan strongly protests to the US side and strongly seeks ​maximum cooperation with the investigation,” as well as the tightening of discipline and thorough ​measures to prevent a recurrence, she said.