Japanese police said Monday they have arrested a 24-year-old US sailor on suspicion of raping a Japanese woman on Okinawa, in a case that could further fan sentiment against Washington's military presence on the fortified southern island. Okinawa was the site of a brutal World War II battle between Japan and the United States but is now considered a strategic linchpin supporting the two countries' decades-long security alliance. Pacifist sentiment, however, runs high on the crowded island, which makes up less than one percent of Japan's total land area but is home to about 75 percent of US military bases in the country. More than half of the 47,000 American military personnel in Japan are stationed there and rapes and other crimes by US service personnel have sparked local protests in the past. A spokesman with the Okinawan prefectural police on Monday identified the arrested seaman as Justin Castellanos, stationed at the US Marine Corps Camp Schwab base on the island. Castellanos, arrested Sunday, allegedly raped the woman earlier the same day while she was unconscious at a hotel in the Okinawan capital city of Naha, the spokesman said. A spokesman for the US Navy in Japan had no immediate comment on the arrest. Chief Cabinet Secretary Yoshihide Suga, the Japanese government's top spokesman told reporters that the alleged incident is "extremely regrettable". Suga said the Japanese government had "expressed a strong protest" to the US side, adding he hopes that police can solve the case. "The US side said it would be a very disappointing incident if the allegation was true and that they're taking this matter seriously," he added, referring to what he described as the US response to Japan's protest. Takeshi Onaga, the governor of Okinawa, expressed anger at the alleged rape. "It was a serious crime in violation of women's human rights and can never be tolerated," he said, according to Kyodo News agency. "I feel strong resentment." According to Japanese media, the sailor found the woman, who was visiting Okinawa, asleep in the corridor of the hotel and took her to his room. The two were staying at the same hotel, but were not acquainted, the Asahi Shimbun daily and other media said. A brutal 1995 abduction and rape of a 12-year-old girl on Okinawa by three US servicemen sparked massive protests, which led the US government to pledge efforts to strengthen troop discipline to prevent such crimes and reduce its footprint on the island. But continued crimes by US personnel remain an irritant in Japan-US relations and a rallying point for Okinawans opposed to the bases.