India's military vowed Wednesday to press ahead with evacuations from the country's flood ravaged north after 20 airmen and paramilitary members were killed when their helicopter crashed during a rescue mission.

Soldiers, backed by some 60 helicopters, were leading the rescue of thousands of Hindu pilgrims and tourists still stranded after flash floods and landslides hit the Himalayan state of Uttarakhand, killing some 1,000 people.

One of the helicopters, carrying soldiers, police and rescue workers, crashed on Tuesday afternoon near the temple area of Kedarnath, which has become the epicentre of the disaster.

"Twenty warriors have died. It is a loss for the entire nation," Air Chief Marshal NAK Browne, the head of the airforce, said in the state capital Dehradun, adding that an investigation was under way into the cause of the crash.

"We have to finish the mission and finish it right. We will make sure that the job is done," he said during an inspection of rescue operations.

Raging rivers swept away houses, buildings and even entire villages on June 15 after torrential rains hit the state, which was packed with tourists and pilgrims travelling to Hindu shrines. More than 1,000 bridges have been damaged along with roads, cutting off villages and towns.

Survivors have recounted harrowing stories of their loved ones plummeting to their deaths or being washed away in the deluge.

Shachi Dobhriyal said she watched helplessly as her family of nine was swept away by the waters, as she clung to a wooden bar in a hotel in Ram Bada, a base camp for pilgrims travelling to Kedarnath.

"What can I say? I lost my two children, husband, nephews and my in-laws. The river swallowed them alive," the 45-year-old told AFP from a hospital bed in Dehradun where she is being treated for trauma.

Manish Kumar, 45, said he was trying to walk out of the remote Jungle Chatti area near Kedarnath shrine with his wife and six-year old son when a landslide hit the road.

"We were trying to cross one of the badly-damaged roads by foot two days after the rains struck," Kumar told AFP.

"Suddenly there was a massive landslide. My wife fell into a deep gorge and I could do nothing to save her," he said, holding his son in his arms.

Kumar, who was eventually rescued by an army chopper and brought to Dehradun, refuses to return home in Jabalpur in the central state of Madhya Pradesh in case his wife is found.

Officials said close to 100,000 people have been evacuated so far from the mountainous region but some 6,000 remain stranded. Bad weather has hampered rescue efforts in recent days but evacuations were stepped up Wednesday as well as food and other aid drops to those stranded.

"Approximately 100 people are being evacuated by the choppers per hour," the state government said in a statement.

Rescue officials are becoming increasingly concerned about the spread of disease, particularly from the decomposing bodies of those who perished in Kedarnath and other pilgrimage areas.

Preparations have been made for mass cremations with tonnes of wood and ghee, used in Hindu funeral rituals, transported to remote areas. Cremations were delayed on Tuesday because of heavy rains and authorities said the cremations should began "as early as possible."