At least 20 people were feared dead after suspected militants opened fire on them in India's Himalayan territory of Jammu and Kashmir on Tuesday, with officials saying it was one of the deadliest such attacks in recent times.

The region's chief minister said the attack was "much larger than anything we've seen directed at civilians in recent years".

A group of gunmen shot and killed at least 26 domestic tourists and others and wounded many in the Baisaran Valley tourist town of Pahalgam, Kashmir, on Tuesday morning.