A speedboat carrying Indian tourists capsized off southern Vietnam’s Phu Quoc island on Saturday, killing at least 15 people, state media reported.

The boat was carrying 36 people when it overturned around 400 metres off May Rut Ngoai islet, according to the VNExpress website.

Multiple tourist and coast guard boats participated in a rescue effort during which some people were plucked safely from the water.

The Tuoi Tre newspaper quoted local police as saying 21 people had been transported to a hospital for emergency treatment, two of whom were in critical condition.

India’s embassy in Vietnam confirmed the capsized boat had been carrying “several Indian tourists” but said that “exact details of the incident are being ascertained”.

Nguyen Tien Hai, a provincial official of the ruling Communist Party, said authorities were still confirming the exact number of survivors, according to the state media report.

Hai said initial assessments suggested that the speedboat may have overturned due to heavy winds and high waves.

Located just south of Vietnam’s largest island Phu Quoc, May Rut Ngoai is known for its pristine blue waters, white sand beaches and accessible diving reefs.

Visitors often access the islet by speedboat from the main island.

Phu Quoc has seen a major tourism boom in recent years, with more than 1.8 million foreigners visiting the island last year.

Boating accidents are a regular occurrence in Vietnam, where extreme weather, persistent flooding and inadequate maintenance have led to frequent tragedies.

In July last year, 39 people were killed when a tourist boat ferrying families around northern Vietnam’s famed Ha Long Bay capsized after being lashed by a sudden storm.