The search for survivors in northwestern China is growing desperate in the wake of flash floods and landslides that have killed hundreds and disrupted the lives of millions more across Asia.

In one of the most dramatic cases, a landslide in China's Gansu province took out an entire village.

Rescuers were digging through mud and wreckage there on Monday using shovels or their hands, CTV's Beijing Bureau Chief Ben O'Hara-Byrne reported. In one instance, rescuers were able to pull a 74-year-old woman from the rubble of her home.

"But overall survivors are saying they don't think very many people escaped this landslide that crashed into the town at midnight Saturday, when very many people were sleeping," O'Hara-Byrne said. "There are very few signs of optimism today."

Officials estimate that landslides in Gansu province have killed 337 people, covering villages in water and mud. But the number of dead is likely to climb as rubble is removed, with 1,148 people reported missing by Monday night, local time. About 45,000 people have also been relocated on evacuation orders.

Meanwhile in Pakistan, flooding has killed 1,500 people. An estimated 13.8 million people have been affected by the country's worst-ever flooding, leading to widespread concerns of an impending humanitarian disaster.

In the Indian-controlled mountainous Kashmir district, rescuers came to the aid of foreign hikers and to search for 500 people missing in flash floods there that killed at least 140.

China's Gansu landslide was caused by a blockage of the Bailong River, which created a three-kilometre-long artificial lake. It overflowed early Sunday morning, crashing down into the town below, which is located in the remote county of Zhouqu.

Apartment buildings were demolished, houses uprooted and more than a metre of mud and silt was dumped on the streets, The Associated Press reported.

Vehicles were trucking aid supplies over congested roads, attempting to reach survivors in the area, while bodies taken from the rubble were wrapped in blankets and laid out on truck beds.

"There were some, but very few, survivors. Most of them are dead, crushed into the earth," said Guo Wentao, who witnessed the disaster.

O'Hara-Byrne said there was some positive news Monday as officials were able to get heavy equipment into the landslide-hit area to help with rescue efforts.

State broadcaster CCTV beamed video of Premier Wen Jiabao at one of the devastated areas.

"Don't move! We're getting you out," he called out to a group of people waiting to be rescued from their buried home.

Demolition crews tried to clear debris blocking the Bailong River upstream from Zhouqu to prevent more devastation. Work is also underway to restore power and communication lines to the affected areas.

However, more rain is forecast for early in the week, which could add to the misery of residents.

"Already most have been evacuated but you can imagine if more bad weather and more rain were to come and more water were to come down it would seriously hamper an already very difficult rescue effort," O'Hara-Byrne said.

The floods in northwest China have caused tens of billions of dollars in damage across 28 provinces and regions. So far this year 1,100 people have perished in what is being called the country's worst flooding in a decade.

In Pakistan, the United Nations said flooding may affect more people than the 2004 Indian Ocean tsunami, the 2005 Kashmir earthquake and the 2010 Haiti quake combined.

Maurizio Giuliano, spokesman for the UN Office for the Coordination of Humanitarian Affairs, said that rescue workers were still trying to reach as many as 600,000 people stranded in the northwestern Swat Valley.

There is growing frustration at the government's response to the crisis across Pakistan. Islamabad has deployed thousands of troops to distribute aid but they have been overwhelmed by the extent of the catastrophe, leading to fears of a humanitarian disaster.

Manzoor Ahmed fled his home in Sindh province in the south of the country, along with thousands of other survivors.

"It would have been better if we had died in the floods as our current miserable life is much more painful," the 25-year-old said, after spending the night shivering in the rain with his family.

With files from The Associated Press