TOKYO - SEVEN South Korean and nine Indonesian sailors are missing after two commercial ships collided off Japan early on Tuesday, the Japan Coast Guard said.

The South Korean-flagged Orchid Pia and Panamanian-flagged Cygnus Ace, collided at about 2.15am (1715 GMT Monday, 3.15am Singapore time) in waters off Izu Oshima Island, roughly 120km south of Tokyo, the coast guard said.

The 10,833-tonne Cygnus Ace immediately reported the incident to the coast guard and said its radar was not able to locate the South Korean vessel.

The 4,255-tonne-Orchid Pia has not responded to radio signals from the coast guard, which has launched six patrol vessels and two planes to search the freighter.

The ship, carrying 16 crew members and 5,051 tons of steel coils, was travelling from the port of Kashima in eastern Japan to South Korea, the coast guard said.

'It is possible that Orchid Pia sunk,' a coast guard official said.

'We found an empty raft in the area waters, but so far we are continuing the search for the missing individuals,' he said.

Cygnus Ace suffered some damage but is able to navigate, the coast guard said. There are no reports of sailors missing from the ship. -- AFP