TOKYO, Japan: American troops stationed on Japan's Okinawa island have been placed under a month-long curfew and banned from drinking alcohol following the alleged murder and robbery of a local woman by a U.S. Marine.

Lance Corporal Devin Jacob Ballard, 20, is suspected of killing 39-year-old Anna Yagi in a hotel in Naha, the capital of Okinawa prefecture, on October 3. He is also accused of taking her wallet and backpack. Police said Ballard denied the allegations.

The case has renewed long-standing concerns in Okinawa about the large U.S. military presence on the island, which is close to Taiwan and China. A series of incidents involving U.S. personnel has caused tensions with local residents and raised concerns about the impact on Japan-U.S. relations.

U.S. military authorities ordered all troops on Okinawa to follow a curfew for one month and banned them from drinking alcohol during the period.

All U.S. military operations on the island will also be suspended for 48 hours while troops receive training on discipline and standards.

Lieutenant General Benjamin Watson said the measures were needed to protect trust between U.S. forces and local communities.

"Every interaction with our neighbors either builds or undermines the trust that is essential to our team," Watson said.

Japanese Prime Minister Sanae Takaichi described the killing as extremely brutal and serious. She said Japan had strongly protested to the United States and demanded steps to prevent similar incidents.

Police told the Stars and Stripes newspaper that Yagi died from asphyxiation after Ballard allegedly pressed on her neck.

Hotel staff found Yagi unconscious in her room early on October 3 after she failed to check out. Local media reported that about 200 police officers took part in the search for Ballard after CCTV footage showed him entering the hotel with Yagi.

The killing has led to protests in Naha and Tokyo. Okinawa hosts a large part of the U.S. military presence in Japan. Most of the roughly 18,000 U.S. Marines based in Japan are stationed there.

The latest killing could create further difficulties for Takaichi's plan to move some U.S. Marines from the crowded Futenma air base to a less populated facility at Henoko. Opponents of the plan want the U.S. military presence removed from Okinawa altogether.

Okinawa is about 100 kilometers from Taiwan at its closest point. Japan and the United States consider the island strategically important for deterring possible Chinese military action.