A leak from a damaged oil tank in a Japanese ship has stopped, the Mauritius prime minister's office said on Monday, adding that the situation was still very serious and they were preparing for "a worst case scenario".

The MV Wakashio, owned by the Nagashiki Shipping Company and operated by Mitsui OSK Line still has 2,000 tonnes of oil aboard its two undamaged tanks, the office said, citing a speech given live on television.

Several cracks have been seen on the hull of the grounded oil tanker and the ship will fall apart eventually, Pravind Jugnauth said in the speech.