Pakistan says over 18,000 people are dead and 41,000 injured from the huge earthquake that hit the region, describing it as the biggest disaster in the nation's history.

Military spokesman Major General Shaukat Sultan also warned the number of casualties from Saturday's quake, which measured 7.6 on the Richter scale and also caused fatalities in India and Afghanistan, would rise significantly as entire villages and towns had been wiped off the map.

"It is the biggest ever disaster in the history of Pakistan," Sultan told AFP, appealing for massive international aid.

Sultan said military helicopters were leading rescue efforts in the worst affected zones, the rugged terrain of the North West Frontier Province and the towering Himalayan mountains of the Pakistani-controlled zone of Kashmir.

"Village after village has been wiped out," said an official in Muzaffarabad, the main town in Pakistani Kashmir. "The Neelum River has been blocked because whole villages have fallen into the water."

The scale of the disaster has shocked the international community and brought pledges of aid and expressions of sympathy.

The earthquake struck just as schools were beginning morning classes and hundreds, perhaps thousands, of children died when cheaply-built concrete buildings collapsed or were engulfed by landslides.

"There is no hope of survival for some 350 children who were trapped in the debris in three schools here," said Yameen Khan, police chief of Mansehra, one of the worst-hit districts.

"All the children from our village went to Balakot and only one of them has come back," said Abdul Rashid, a local official in the village of Shawal.

Near the shattered town of Balakot in NFWP, the scene was one of total devastation with many villages lying in ruins.

Landslides blocked the steep mountain roads and powerful aftershocks sowed terror among survivors, dislodging huge boulders from further up the hillsides. Rain, hail and freezing temperatures added to the misery.

Officials said surgeons were being dispatched to Kashmir along with nine helicopter loads of emergency aid. They said bad weather and the destruction of infrastructure was severely affecting relief efforts.

The quake also killed at least 320 people and injured 700 in the Indian zone of Kashmir, said the state's chief secretary Vijay Bakaya, warning the toll would rise.

The epicentre was close to the dividing line between Indian and Pakistani controlled zones of Kashmir, and scores of soldiers on both sides died when their heavily-fortified positions collapsed around them.

The US Geological Survey and the Pakistan Meteorological Department said the quake measured 7.6 on the Richter scale while the Japanese Meteorological Agency put it at 7.8.

PHOTO CAPTION

Villagers wait on the side of a road for bodies of earthquake victims to be transoprted to a burial site in the village of Boly. (AFP)