Thousands of Hindu devotees from across India began trekking up through Himalayan passes in Indian-administered Kashmir on Saturday, for the start of an annual pilgrimage accompanied by a major security escort.

Critics accuse India's Hindu nationalist government of using the annual Amarnath procession to reinforce New Delhi's claims over the disputed Muslim-majority region.

The pilgrimage is a journey to a cave shrine at an altitude of 3,900 metres (12,795 feet) that contains a holy stalagmite, believed to be an incarnation of the deity Shiva.

Tens of thousands of soldiers, paramilitary troops and police were deployed along two separate routes leading to the remote destination.

"Every soldier has been briefed to ensure (the) least inconvenience to locals," army officer Amandeep Malhi told reporters on Friday.

Last year, at least 16 pilgrims died in flash floods that struck near the cave, and Malhi assured pilgrims that his forces would be ready if disaster struck again.

"This year, quick and effective response teams will ensure fast evacuation in case of any natural calamity," he said.

The pilgrimage used to be low-key, with a few thousand pilgrims attending, until an armed insurgency against Indian rule in Kashmir erupted in 1989.

Since then, the religious practice -- and accompanying security mobilisation -- have grown, as has its political significance.

Kashmir is divided between India and Pakistan and claimed by both.

Rebel groups fighting for Kashmir independence have often said that the pilgrimage is not a target but have warned in the past that if the religious event was used to establish Hindu domination of the territory they would act.

In 2017, suspected rebels attacked a bus, killing 11 pilgrims.

AFP