Protesters demonstrate outside the Kadena Air Base in Okinawa, Japan, on May 20. (Hitoshi Maeshiro/European Pressphoto Agency)

The U.S. Navy on Monday banned its sailors on the Japanese island of Okinawa from drinking alcohol, both on and off base, and placed tight restrictions on their movement after a sailor was arrested on suspicion of drunken driving.

Petty Officer 2nd Class Aimee Mejia was arrested after she was involved in a crash on Okinawa’s main island this weekend, in the midst of a month-long curfew imposed on U.S. service members after the arrest of an American contractor on murder-related charges.

The latest incident is likely to further inflame local anger over the U.S. military presence on the island, which shoulders the overwhelming burden of the U.S.-Japan military alliance.

Mejia, 21, crashed head-on into two cars after crossing the center line on a highway shortly before midnight Saturday, according to a police spokesman.

The sailor was unhurt, but a 35-year-old woman and a 30-year-old man in the other cars were injured, one suffering a chest injury, the other an arm injury.

U.S. Naval Forces Japan immediately banned all drinking of alcohol by its sailors and said they would be allowed off base only to “engage in official actions” such as taking their children to child care or going to the grocery store or gas station.

“These measures are not taken lightly,” said Rear Adm. Matthew Carter, commander of Naval Forces Japan. “For decades, we have enjoyed a strong relationship with the people of Japan. It is imperative that each sailor understand how our actions affect that relationship, and the U.S.-Japan alliance as a whole.”

The measures will remain in place until commanders are “comfortable that all personnel understand the impact of responsible behavior on the U.S.-Japan alliance,” he said.

Mejia, who serves at Kadena Air Base in Okinawa, was found to have a blood alcohol level about six times the legal limit during a breath test, officers from the Kadena police station told Kyodo News.

She is in Japanese police custody, and the U.S. military is cooperating fully with the investigation, said Lt. Gen. John Dolan, commander of U.S. forces in Japan.

The incident occurred during a month of “modified liberty regulations” for U.S. military personnel, designed as a time of “unity and mourning” over a brutal killing on the island.

Kenneth Shinzato, a 32-year-old former U.S. Marine who was working as a computer and electrical contractor on the Kadena base, was arrested last month in the slaying of 20-year-old Rina Shimabukuro.

Shimabukuro’s body was found in a forest near where Shinzato told police they would find her, according to local news reports. She appeared to have been stabbed and strangled, they said.

Shinzato, who is married to a local woman and took her surname, has been charged with dumping a body, often a precursor to a murder charge.

After the slaying, U.S. military personnel and civilian employees, as well as their families, were prohibited from drinking or buying alcohol outside U.S. bases, going to parties off base or being off base between midnight and 5 a.m. until June 24.

Tensions are running high on Okinawa, which makes up only 1 percent of the Japanese land mass but is home to several huge military bases and more than half of the 50,000 U.S. troops in Japan.

There is sizable opposition on Okinawa to attempts to relocate a controversial U.S. Marine Corps base to a new site on the island, with many calling for the facility’s closure.

In prefectural elections on Sunday, candidates who oppose the relocation triumphed, taking 31 of 48 seats, according to Kyodo. The base has long been viewed as a source of crime, danger and noise.

After the killing of Shimabukuro, local newspapers started publishing detailed histories of U.S. military misbehavior in the prefecture.

The Okinawa Times reported last month that 5,862 U.S. military personnel and civilian employees were arrested between 1972 and 2014, 737 of them in serious crimes, including murder, rape, burglary and arson.

Meetings with a U.S. congressional delegation that visited Okinawa last week were canceled because local politicians did not want to be seen dealing with U.S. representatives, delegates said.

At the Asia Security Summit in Singapore, Japanese Defense Minister Gen Nakatani called the latest incident “extremely regrettable.” He told reporters that he had instructed officials at the Okinawa Defense Bureau to lodge a formal complaint with the U.S. Navy in Okinawa.

Before the incident, Nakatani had met with U.S. Defense Secretary Ashton B. Carter and asked him to ensure that all U.S. military personnel and contractors “consciously abide by Japanese laws.”

In Tokyo, Foreign Minister Fumio Kishida called U.S. Ambassador Caroline Kennedy and again asked the United States to do more to prevent such crimes. The U.S. Embassy in Tokyo had not commented by Monday morning.