Tokyo:The US will hand back 4,000 hectares of land currently being used for American military bases in Okinawa to Japan, the authorities have announced. The land represents 17 per cent of the US Army-controlled territory in Japan, making it the biggest land return since Japan recovered from Washington the administration of Okinawa, the scene of a Second World War battle which claimed 240,000 lives, EFE news reported. However, the American authorities did not specify when the land -- used for jungle combat training -- will be returned. "Once facilities or areas are no longer necessary to meet those ends, they will be returned to the Japanese government," said the armed forces in a statement released on Friday. Once several helipads constructed, it will allow nearly 4,000 hectares of land to be returned to Japanese authorities, the statement added. Okinawa houses more than half of the nearly 47,000 troops that the US maintains in Japan, as well as 74 per cent of military facilities in the island country. Okinawa residents have protested for years over the deployment of US forces to the island, with dissent heightening whenever crimes alleged to be committed by US security personnel or workers occurs. One of the most serious recent incidents took place in May this year, when Japanese police arrested a former US marine working at the Kadena base over allegations that he raped and murdered a 20-year-old Japanese woman.