At least seven vehicles were destroyed, including six trucks and a minivan. But Xinhua said the number of vehicles that fell into the river remained unclear as the remote area was not covered by telecommunications signals.

The death toll could rise later as more vehicles were recovered from the river, Xinhua reported.

Pictures from the scene showed vehicles hanging off the collapsed bridge, while photographs on scol.com.cn, a news portal run by the Sichuan government, showed at least one person trapped in the bridge's structure.

By last night, at least six people had died and 12 more were injured and in hospital, five of them in a serious condition, scol.com.cn reported.

The bridge was a crucial route linking Wenchuan to Dujiangyan city.

It is part of National Highway 213 and considered vital to the restoration of Aba prefecture.

The highway also links Chengdu to the famous Jiuzhaigou National Park.

An Aba prefecture propaganda office official told the news portal that traffic congestion was common on the bridge due to the high number of trucks transporting materials for reconstruction work in the area.

Xinhua said more than 10,000 vehicles crossed the bridge every day. It was closed for a year after it was hit by rocks during the magnitude-8 earthquake in May last year, which left 87,000 people dead.

The report did not give any further details on the circumstances of the accident, which occurred after heavy rain battered the province and other parts of the mainland.

At least four people were killed and 50 missing after a landslide on Thursday in the Kangding district of Sichuan.

A mud and rock slide triggered by heavy rain buried the encampment of a road construction crew, state media reported.

Various provinces have been hit by flooding and heavy rainstorms in recent weeks. For the past two days, rainstorms have struck Huaihua city, Hunan province, killing at least four people, while five more were missing.