Authorities Friday ended search and rescue operations for any survivors trapped in the rubble of last week's earthquake, and thunderstorms forecast for the region threatened to disrupt relief efforts for millions left homeless and hungry by the disaster.

Aid workers held mass burials and rushed to set up tent camps for an estimated 2 million homeless before the rains hit in the Himalayan region of Kashmir (search).

With Pakistan's death toll estimated at more than 35,000, officials said there was virtually no hope of finding more people beneath tens of thousands of collapsed buildings.

India has reported more than 1,350 deaths on the side of Kashmir it controls from the magnitude-7.6 quake on Oct. 8.

"The first phase is search and rescue. As a phase, that has now ended," said Jan Egeland (search), the U.N. undersecretary-general and emergency relief coordinator. "It's a cruel reality. But after a week, very few people survive."

Added U.N. spokesman Winston Chang: "We are all of the view that there is a less than 1 percent chance of survival on the seventh day."

At a news conference in Islamabad, Egeland said aid agencies were now focusing on providing food and shelter to the millions who need it.

Egeland, who has traveled to the hardest-hit areas, also said coordination among the hundreds of aid groups in the quake zone was vital to the relief effort.

"If we don't work together, we will become a disaster within a disaster," he said. "It will take billions of dollars to rebuild. ... This will take five to 10 years."

Mohammed Hanif, a senior meteorologist in Islamabad, said rain was expected in the capital, in Kashmir and in other parts of the country.

"Rains with thunderstorm will definitely disrupt relief operations in earthquake-hit areas," he said.

Earlier this week, heavy rains and hailstorms grounded helicopters flying food and other supplies to devastated areas, and snow has already started to fall in some areas of Kashmir.

During an earlier visit to the devastated city of Muzaffarabad (search), the capital of Pakistani Kashmir, Egeland said millions urgently need food, medicine, shelter and blankets.

"I fear we are losing the race against the clock in the small villages" cut off by blocked roads, he said. "I've never seen such devastation before."

Many exhausted relief workers were dealing with the added burden of fasting during daytime hours for the Muslim holy month of Ramadan (search).

Maj. Farooq Nasir, an army spokesman in Muzaffarabad, said the search and rescue operation had ended. Army officials in Balakot, another of the hardest-hit towns in northwest Pakistan, said they were shifting the rubble of collapsed buildings and removing dead bodies.

Water and electricity were restored to parts of Muzaffarabad, a city of about 600,000. Authorities were also working to fix grid stations to bring power back to outlying villages.

The country's relief commissioner, Maj. Gen. Farooq Ahmad Khan, said Pakistan expected to get 2 million blankets and 100,000 large tents before the onset of winter. He said 200,000 houses had been destroyed.

From daybreak, Pakistani military helicopters and choppers from other countries flew in and out of a sports stadium in Muzaffarabad, where a temporary hospital had been set up. The choppers carried out injured people from remote villages and ferried aid workers to isolated regions.

The U.S. military has deployed 13 helicopters — eight Chinooks, three Black Hawks and two heavy-lifting MH-53s — to ferry rescue workers and supplies to the quake zone, and has begun dropping relief supplies by air from C-130s. It also prepared to send a 36-bed Mobile Army Surgical Hospital (search) from Germany, and a water purification crew.

U.S. aircraft and troops will assist in relief efforts in Pakistan as long as they are wanted, the commander of the U.S. military's disaster assistance center said Friday.

"My view is that we will be here as long as Pakistan wants us, to demonstrate our friendship," U.S. Navy Rear Adm. Michael Lefever said.

Dozens of countries have donated money and aid. New Zealand doubled its earthquake aid to $1 million and Japan dispatched 100 troops and two military transport planes carrying a helicopter and a power-supplying vehicle.

In the Pakistani town of Balakot, dozens of volunteers burrowed into a collapsed school and dug mass graves. They complained that Pakistani soldiers were not helping.

"We got 25 bodies of children yesterday and buried them in a mass grave. We got seven more today," said volunteer Sayed Ahmad Hussain, 35.

"We still expect miracles," Hussain said. "But the bodies we pulled out were in bad shape ... they are now decomposing."

A relief team from Britain-based Plan International flew a helicopter carrying water, juice and milk to villages in the Mansehra district of North West Frontier Province and said people were hungry and panicking.

In Islamabad, police launched a criminal investigation into the collapse of a 10-story luxury apartment tower that toppled during the quake, killing at least 40 residents. It was the only structure that collapsed in the capital.

Millions of Muslims thronged mosques across Pakistan on Friday, the Muslim sabbath, to pray for those who died in the earthquake.

"God, forgive us," said Mulana Sazluddin Chishdi, the cleric of a damaged mosque in the center of Muzaffarabad, where 1,500 worshippers gathered. "Help all those who are helping others in this hard time, and give the nation courage to bear this loss."