More than 1,000 tonnes of fuel have seeped from the bulk carrier MV Wakashio into the azure sea off southeast Mauritius, befouling the coral reefs, white-sand beaches and pristine lagoons that lure tourists from around the globe.

But another 2,500 tonnes remain aboard the stricken vessel, which ran aground on a reef but only started oozing from a crack in the hull in the past week.

Prime Minister Pravind Jugnauth on Sunday said response crews had managed to stymie the leak for now but were bracing for the worst.

Mitsui OSK Lines, which operates the vessel owned by another Japanese company, promised on Sunday to “make all-out efforts to resolve the case”.

“We are terribly sorry,” the shipping firm’s vice president, Akihiko Ono, told reporters in Tokyo.