U.S. military helicopter crashes in waters off Okinawa

The Japanese Coast Guard said it was helping to look for crew from the helicopter. The U.S. Forces, Japan had no immediate comment.

The accident comes as Japan's central government begins talks with Okinawa's governor over contentious plans to relocate a U.S. Marines air base to a less crowded part of the island, host to the bulk of U.S. military forces in Japan.

Residents of Okinawa, the site of bloody battles between U.S. and Japanese forces near the end of World War Two, have long objected to tens of thousands of U.S. troops and U.S. military installations on 18 percent of their island.

Japan's central government earlier this month suspended construction of a replacement facility for the U.S. Marines' Futenma air base for a month to give time for talks between Tokyo and island authorities opposed to the base.

The island's governor, Takeshi Onaga, won office last year largely on his stand against U.S. bases, and has accused Prime Minister Shinzo Abe of looking down on the island's people.

Chief Cabinet Secretary Yoshihide Suga was in Okinawa on Wednesday to meet with Onaga.

The suspension of construction had been intended to take the emotive issue off the table while the government pushes sensitive security bills through parliament.

The legislation, which could allow Japanese troops to fight overseas for the first time since World War Two, has passed parliament's lower house and is being debated in the upper chamber, but it has dragged down Abe's support rate to less than 40 percent because of public concerns over the policy shift.

(Reporting by Linda Sieg, Elaine Lies, Nobuhiro Kubo and Kaori Kaneko)