Japan demanded the U.S. Monday to toughen discipline among its servicemen after an American sailor allegedly raped a Japanese national in southern Okinawa prefecture. Justin Castellanos, a U.S. Navy seaman, was arrested at Camp Schwab Sunday on suspicion of rape of a 40-year-old tourist in a hotel.

Chief Cabinet Secretary Yoshihide Suga said the sailor’s arrest was “extremely regrettable,” while Okinawa Gov. Takeshi Onaga said that the incident is “a serious crime and blatant violation to women's human rights,” the Associated Press reported. Onaga also expressed concern that the incident could hamper the island’s tourism, which is an important part of its economy.

According to Okinawa police, Castellanos allegedly took the woman to his room after finding her sleeping in the hallway of the hotel and raped her, Japan’s Kyodo News reported. The two stayed at the same hotel but they were not acquainted, the police added. Castellanos has not been formally charged.

The Okinawa Island houses about 75 percent of the U.S. military facilities in the country despite accounting for less than 1 percent of Japan’s total land area. Residents of Okinawa have maintained their disapproval of U.S. troops and U.S. military installations on 18 percent of the island. Most residents blame the U.S. bases for accidents, crime and pollution.

In 1995, the abduction and rape of a 12-year-old girl by three U.S. servicemen triggered protests across the country, ultimately leading to an agreement to relocate the Marine Corps Air Station Futenma to a less crowded part of the island. However, local residents have reportedly demanded that Futenma base should be closed.