Japanese tanker damaged off Oman, cause unclear

One of the 31 crew aboard was injured but no oil leaked from the M Star very large crude carrier (VLCC), according to the Japanese transport ministry.

It said an explosion occurred onboard at around 00:30 a.m. local time (2030 GMT Tuesday), but the cause was unclear.

"A crew member saw light on the horizon just before the explosion, so (ship owner Mitsui O.S.K.) believes there is a possibility it was caused by an outside attack," Japan's ministry said in a statement.

Oman's coastguard said there was no evidence of any attack on the tanker and instead cited an earthquake.

"The boat was hit by a tremor ...we have no information of an attack," an Omani coastguard official told Reuters.

The Strait of Hormuz remained open and it was "business as usual," an official from the Omani ministry of transport said.

Al Qaeda has threatened to attack shipping in the Strait of Hormuz, a route used by some 40 percent of the world's seaborne oil.