Tokyo ( CNN ) -- Japanese officials expressed outrage after two U.S. sailors were arrested over accusations that they raped a woman on the island of Okinawa , where the American military presence has generated long-simmering resentment . Defense Minister Satoshi Morimoto on Wednesday called the alleged rape `` vicious and mean '' and said Japanese authorities were lodging protests with the U.S. government and military , as well as demands for better preventive measures . Okinawa Gov . Hirokazu Nakaima , who met with Morimoto over the matter , said it went `` beyond madness '' that the alleged attack took place two months after a U.S. Marine was arrested over accusations he assaulted and molested a woman in Naha , the capital of Okinawa . Police in Okinawa identified the detained sailors as U.S. Navy Seaman Christopher Daniel Browning and Petty Officer Skyler Dozierwalker of Naval Air Station Joint Reserve Base Fort Worth in Texas . The two men , both 23 , are alleged to have raped a Japanese woman in the early hours of Tuesday morning , leaving her with an injury to her neck , police said . They were taken into custody later that day . Tensions over the American military presence on Okinawa have boiled over before . Many residents were incensed by the rape of a 12-year-old Japanese girl in 1995 by three U.S. military personnel . And allegations that a Marine raped a 14-year-old girl caused a furor in 2008 , although the girl decided not to pursue charges . About half of all U.S. military personnel in Japan are stationed in Okinawa . The U.S. government is `` extremely concerned '' by the allegations against the two service members , U.S . Ambassador to Japan John Roos said in a statement Tuesday . `` We are committed to cooperating fully with the Japanese authorities in their investigation , '' he said . Japanese Vice Foreign Minister Shuji Kira on Wednesday summoned Roos over the case , urging the enforcement of stricter discipline and preventive measures . Morimoto , the defense minister , suggested that if the Japanese protests about the matter did n't prove effective enough , he could raise the issue with U.S. Defense Secretary Leon Panetta . Opposition to the presence of U.S. troops in Okinawa runs so deeply that it contributed to the resignation of former Prime Minister Yukio Hatoyama in 2010 . He had promised to move a U.S. base but later announced that it would stay . His critics said at the time that he gave in to U.S. pressure , and his governing coalition broke up . As well as the cases of misconduct by U.S. troops , some Okinawan residents have complained about issues such as environmental and noise pollution from the American presence . There is also concern in Okinawa about the U.S. deployment of the Marine Corps MV-22 Osprey , a controversial tilt-rotor aircraft that can take off and land like a helicopter but fly like an airplane . Doubts about the Osprey 's safety have been fueled by two crashes -- one in Morocco and one in Florida -- earlier this year . The United States and Japan announced in April that nearly half the 19,000 U.S. Marines on Okinawa would leave soon and relocate to other areas in the Asia-Pacific region , including Guam , Hawaii and Australia .
NEW : Japanese defense minister says they are lodging protests with Japanese authorities . The two year - olds are accused of killing a Japanese woman on Okinawa . Questions over the U.S. military presence on Okinawa have boiled over in the past . The U.S. government is ` ` extremely concerned '' by the allegations , he says .