Thousands flee as slip blocks Nepal river

Thousands of panic-stricken villagers have fled homes fearing flash floods after a landslide blocked a river in quake-hit Nepal's mountainous northwest.

The late-night slip has sent mud and rocks tumbling into the Kali Gandaki river in Myagdi district, causing water levels to rise 150 metres.

"We have evacuated about 100 people. People in other villages don't need immediate rescue but thousands have left on their own," local official Yam Bahadur said on Sunday.

As fresh slides dumped debris into the river during the day, a two-kilometre-long artificial lake created by the blockage began to overflow the newly created dam, home ministry spokesman Laxmi Prasad Dhakal told news agency AFP.

"The artificial lake has begun to overflow the dam ... but there does not appear to be any risk of flooding," Dhakal said.

Soldiers and geologists aboard an army helicopter reached the site early on Sunday and officials were monitoring the water flow closely, Dhakal said.

"Once the soft soil flows away, security forces might blast holes into the hard rocks blocking the river but we have to be very careful," he said.

The region has witnessed several small recent slides, said local official Trivikram Sharma.

"After the two quakes, villagers have reported several minor landslides and late last night they said the hill just came down," Sharma said.

"We cannot immediately assess the risk of flash floods but people are obviously scared that the artificial dam will burst suddenly and submerge their homes."

Police have issued an alert for those living along the river, which begins near the Nepal-China border and flows into northern India, eventually joining the Ganges.

The snow-fed waters are also the site of Nepal's largest hydroelectric project.

Twin quakes in Nepal have left more than 8600 people dead and thousands in desperate need of food, clean water and shelter.