A ship that ran aground off the coast of Mauritius has leaked more than 1,000 tonnes of crude oil into the Indian Ocean.

The island nation has declared a “state of environmental emergency” after the MV Wakashio vessel began to spill out oil at the end of last week.

It is estimated the tanker has leaked about 1,300 tonnes of oil into the ocean so far, but it was reportedly carrying up to 4,300 tonnes.

There are fears more oil could leak into the water as cracks open in the Japanese tanker.

At the weekend, locals donned hazmat suits in an effort to clean-up the area.

The tanker ran aground on a coral reef on 25 July but began leaking oil on 6 August.

Mauritius prime minister Pravind Jugnauth declared the state of environmental emergency on Friday.(Yahoo News)