Critics say the government was too slow to act when the Japanese owned ship carrying 4,000 tonnes of fuel aboard ran aground off Pointe d'Esny, an ecological jewel fringed by idyllic beaches, colourful reefs and protected wetlands.
The spill was declared an ecological disaster for the Indian Ocean archipelago, and a massive clean up operation was launched to scrub the pristine coastline and azure seas of thick sludge.
The collision between the tugboat and an unmanned barge which it was towing occurred off the northeast coast as the boats were returning from the spill site where the MV Wakashio ran aground, the barge operator Taylor Smith Group said.
Jugnauth said the tug was transporting some fuel at the time "but there is no risk of a leak". The prime minister promised an investigation into the accident.