At least 1,000 students and teachers were killed or buried in the collapse of another school in quake-hit southwestern China, state media reported on Tuesday.

"So far, the number of dead or missing is estimated at more than 1,000" at the school, Xinhua news agency said in a dispatch from Beichuan county, where reports earlier had said up to 5,000 people in the area may have been killed by Monday's 7.8-magnitude quake.

More than 1,000 students and teachers were inside the Beichuan Middle School when its six-to-seven-storey main building was reduced to a pile of rubble, the report said.

While "some" occupants were able to escape in time, most did not, it said.

A crowd of about 2,000 anxious students, parents and local villagers camped out at the scene overnight amid rain as rescue efforts proceeded, it added.

"I just pray my child is safe and sound," one crying mother was quoted as saying.

The report said many parents burst into tears when a rescuer pulled out one girl who had lost her legs.

Beichuan is one of the areas hit hardest by the quake, which has caused deaths across at least four provinces and regions.

Many of the nearly 10,000 deaths have been at schools as the quake struck in the early afternoon when classes were in session.