President Donald Trump tightened America’s sanctions on Iran in May, and the US recently strengthened its forces in the area – saying there was a danger of Iranian attacks.
On Thursday, Iran’s supreme leader Ayatollah Khamenei ruled out any negotiations with the US aimed at easing the tensions.
He was quoted as saying during talks with Japanese Prime Minister Shinzo Abe that he did not see President Trump as being worthy of any exchange of messages.
The cause has not been confirmed.
The Norwegian-owned Front Altair had been “attacked”, the Norwegian Maritime Authority said, leading to three explosions on board.
Wu I-fang, a spokesman for Taiwan’s CPC Corp oil refiner, which chartered the Front Altair, said it was carrying 75,000 tonnes of naphtha and was “suspected of being hit by a torpedo”, although this has not been confirmed.
Other unverified reports suggested a mine attack.