An indefinite curfew was been imposed in two southern towns in Sri Lanka following clashes between two religious groups, police said on Sunday.

Clashes broke out on Sunday in Aluthgama, 60 kilometres south of Colombo, when a group led by Buddhist monks protested a previous attack by a Muslim group on a monk in the area.

Police used tear gas in attempt to disperse the two groups, but some set fire to at least 10 shops, raising tension between groups.

A curfew initially announced for Aluthgama was extended to the adjoining town of Beruwala, a predominantly Muslim area, to prevent the unrest spreading.

The two towns are located on the main road heading to the southern part of Sri Lanka, which has popular tourist destinations.