A Japanese fuel tanker that has leaked more than 1000 tonnes of oil and diesel into pristine waters has split into two parts, local authorities say.

The vessel, MV Wakashio, struck a coral reef near the island of Mauritius in the Indian Ocean in July.

Cracks appeared in the body of the ship after days of pounding waves.

On Monday morning (Australian time), the National Crisis Committee of Mauritius confirmed MV Wakashio has broken apart on the reefs of Pointe d’Esny.

“A major detachment of the vessel’s forward section was observed,” it said in a statement.

The front part of the vessel had drifted about 30 metres, director of maritime affairs Alain Donat told newspaper Le Mauricien.

The front part was supposed to be towed away on Saturday but bad weather delayed the operation.

It is believed to have sunk at least 1000 kilometres off the island nation and comes three weeks after the bulk carrier ran aground on a reef off Mauritius.

A salvage vessel with the broken-up MV Wakashio. Photo: AAP

About 1180 tonnes of its cargo has leaked into the popular honeymoon resort’s pristine coastal waters, forcing Mauritius to declare an environmental state of emergency last week.

Authorities, however, have been accused of being slow to act.

Forty tonnes of fuel oil remained inside the MV Wakashio on Sunday, which authorities were trying to remove before it spilled into the ocean.

A massive clean-up operation involving thousands of local volunteers had been underway.

Japanese Environment Minister Shinjiro Koizumi said on Saturday he was planning to dispatch ministry officials and experts to Mauritius to examine the extent of the damage.

On Thursday, Nagashiki Shipping said it had removed almost all of the remaining 3000 tonnes of fuel oil.

-with agencies