Suspected terrorists sprayed bullets on a passenger bus bringing Hindu pilgrims back from a cave shrine in India-held Kashmir on Monday, killing at least six of them, including five women, and wounding 13 others, police said.

A police officer said the bus was carrying more than 50 people on the annual pilgrimage. He blamed the attack on militants who are fighting against Indian rule in Kashmir.

No group has immediately claimed responsibility for the attack.

The shooting happened near the southern Anantnag town on the main highway linking the India-held Kashmir with the rest of the country. The police officer spoke on condition of anonymity as he was not authorised to talk to reporters.

The pilgrims were returning after paying obeisance at the shrine nestled in the Himalayas at a height of 13,500 feet when they were attacked.

The shooting came despite the deployment of thousands of Indian Army and paramilitary soldiers on the pilgrimage route.

The suspected militants first attacked a police armoured vehicle, and the officers in the vehicle returned fire, a police statement said. “Thereafter, the militants again fired at a police patrol in which a passenger bus was hit by bullets. Six persons died,” the statement said.

India's Prime Minister Narendra Modi condemned the attack and tweeted that “India will never get bogged down by such cowardly attacks and the evil designs of hate.” He also said his thoughts were with all those who lost loved ones in the attack.

“My prayers with the injured,” he tweeted.

The cave is covered with snow most times of the year except for a short period in summer when it is open for the pilgrims. The Amarnath cave houses an ice stalagmite worshipped by Hindus as a symbol of Shiva, the Hindu god of destruction.

Tens of thousands of Hindus take part in the annual pilgrimage which lasts up to one and a half months.

Rebels fighting for decades against Indian rule in Kashmir accuse India of using the pilgrimage as a political statement to bolster its claim on the disputed Himalayan region.