At least 22 people died when a double-decker tourist boat capsized in India's southern state of Kerala, officials said Monday.

The incident happened late Sunday in Tanur, a coastal town in Kerala's Malappuram district. Rescue operations were ongoing.

Dozens of people searched for survivors in and around the stricken vessel during the night, which was partially submerged. Some used ropes to stabilise the vessel while others were in the water, looking inside the boat's windows.

"We have recovered 22 bodies, including 15 females and seven males. There are around six people in the hospital. Rescue operations are on," a police officer from Tanur police station told AFP.

There were around 30 people on board, the officer added.

Local publication Onmanorama reported that 11 people, from a family, including three children, had died in the accident.

The state's sports and fisheries minister V. Abdurahiman, who was helping to coordinate rescue efforts, said most of the victims were children on school holidays.

More than 30 people were believed to be on the vessel at the time of the incident.

Abdurahiman said four people were taken to hospital in a critical condition, according to the Press Trust of India news agency.

Survivors told local media that many of the passengers were not wearing life jackets.

"Pained by the loss of lives due to the boat mishap in Malappuram, Kerala. Condolences to the bereaved families," Prime Minister Narendra Modi said on Twitter, adding that the next of kin of each victim would be entitled to compensation.

It was not immediately clear why the boat capsized.