A Japanese tanker spilled about 4,365 tons of crude oil in the eastern Indian Ocean near the Nicobar islands following a collision with a cargo ship, the tanker's operator announced Tuesday. The spill is believed to be the largest involving Japanese-operated tankers, according a ship owner Mitsui O.S.K. Lines. The Bright Artemis tanker spilled the oil following a collision with the Amar, a smaller cargo ship, Mitsui O.S.K. said in a statement. It said the tanker had maneuvered near the Amar, which was in distress about 500 kilometres west of the Nicobars. Both ships are registered in Singapore. The exact amount of the spill was not clear, the announcement said. The tanker was carrying about 227,000 tons of crude.