All 20 people on board a Indian military helicopter were killed in a crash during a rescue mission for flood victims in the northern state of Uttarakhand.

The aircraft crashed late Tuesday when its rotor blades hit the hillside after rescuing survivors of monsoon floods and landslides that ravaged through the Himalayan region, reports The Associated Press.

Among the dead were five crew members from the Indian Air Force, nine National Disaster Response Force personnel and six Indo-Tibetan Border Police officials, Air Chief Marshal N.A.K. Browne said.

Browne vowed to press ahead with evacuations for about 5,000 people still stranded in the hard-hit state.

“Twenty warriors have died. It is a loss for the entire nation,” Browne said.

“The fact that we’ve lost these lives, we have to finish the mission and finish it right.”

Soldiers, backed by some 60 helicopters, were leading the rescue operations.

About 97,000 people, including many Hindu pilgrims, have been rescued in Uttarakhand, but heavy fog and intermittent rain have complicated efforts.

The devastation swept away thousands of homes, roads and bridges while the death toll has climbed to 1,000.