Shimla, Jul 17 (IANS): Four pilgrims were critically injured when a portion of a glacier collapsed and hit them while they were on the Shrikhand Mahadev yatra, a rock Shiva lingam, in Himachal Pradesh's Kullu district, police said on Wednesday.

The landslide owing to heavy rains has blocked routes, forcing authorities to temporarily halt the pilgrimage that began on July 15.

"A rescue operation was launched after Tuesday night's incident. The injured pilgrims were brought to Parwati Bag where first aid was provided to them," the police said.

About 15,000 pilgrims are expected to pay obeisance to Shrikhand Mahadev this year during the 10-day yatra.

"No devotee is allowed to scale the Shrikhand Mahadev peak, situated at an altitude of 17,600 feet, without medical examination," an official said.

To ensure safety, the pilgrims have to get themselves registered with the police before embarking on the journey. People start their journey from Jaon, some 150 km from state capital Shimla.

The pilgrims negotiate rugged, cold and inhospitable terrain, which takes at least three days and conclude their journey at the Shrikhand Mahadev peak where they pay obeisance to the 72-foot tall Shiva lingam.

Devotees believe that Lord Shiva meditated in Shrikhand and the Pandavas too had trekked to the peak during their 12-year exile.