At least 21 people have reportedly died after a boat capsized in India.

It happened off the coastal town of Tanur in the Malappuram district of India's southern state of Kerala on Sunday.

Reuters news agency reported that the boat was carrying about 40 passengers and capsized because it was overcrowded.

The news agency says the death toll may rise. It says the overturned boat got stuck in muddy waters and was being pulled out to rescue those still trapped inside.