U.S. Marines stationed on Japan’s Okinawa island have been placed under a month-long curfew and prohibited from consuming alcohol following the alleged murder and robbery of a local woman.

Lance Cpl. Devin Jacob Ballard, 20, is accused of killing 39-year-old Anna Yagi at a hotel in Naha, Okinawa’s capital, on Saturday and taking her wallet and backpack. Ballard has denied the allegations, according to Japanese police.

Lt. Gen. Benjamin Watson ordered the restrictions Tuesday, saying U.S. personnel would undergo additional training focused on discipline and standards. All U.S. military operations on Okinawa will also be paused for 48 hours while the training takes place.

“Every interaction with our neighbors either builds or undermines the trust that is essential to our team,” Watson said. “When that trust is damaged, it affects the strength of our alliance and the security of this region.”

Japanese Prime Minister Sanae Takaichi called the killing “extremely brutal and heinous” and said she had strongly protested to the United States while demanding steps to prevent similar incidents.

Japanese police told Stars and Stripes that Yagi died from asphyxiation after the suspect allegedly applied pressure to her neck. Hotel employees discovered her unconscious after she failed to check out, and authorities launched a search after surveillance footage showed a man entering the hotel with her.

The incident has renewed longstanding tensions surrounding the large U.S. military presence on Okinawa. Japan hosts the largest overseas concentration of U.S. forces, with most of the roughly 18,000 U.S. Marines based in Japan stationed on Okinawa.

The island has been the focus of repeated disputes over military aircraft, noise, accidents and alleged misconduct by U.S. personnel. In 1995, the rape of a 12-year-old Okinawan girl by three U.S. servicemen triggered massive protests and renewed calls to reduce the American military presence.

The latest killing could also complicate efforts by Takaichi's government to relocate some Marines from the crowded Futenma air station to a new facility at Henoko. Opponents of the plan have continued to call for U.S. forces to be moved off Okinawa entirely.

Okinawa sits roughly 60 miles from Taiwan at its closest point, making the island strategically important to both Tokyo and Washington as they seek to deter potential Chinese military aggression in the region.

The case has already prompted protests in Naha and Tokyo, while Japanese and U.S. officials continue discussions over measures intended to prevent future incidents and preserve the alliance.