Thousands of Chinese troops rushed to plug cracks in a dam in earthquake-hit Sichuan province but experts later said the site was safe.

The official Xinhua News Agency said 2,000 troops were sent to work on the Zipingpu Dam, upriver from the town of Dujiangyan in the disaster area.

The government later pronounced the dam safe after it was inspected by experts.

"Experts from the Ministry of Water Resources today had a complete and concrete examination on the key sections of the dam," CCTV says, reading a statement also posted on the Sichuan government website.

"After that, the expert group said the structure was stable and safe."

The National Development Reform Commission, China's top economic planning body, says the earthquake had damaged 391 dams.

It says two of the dams were large ones, 28 were medium-sized and the rest were small ones.

'Dam Danger'

In an earlier report, Xinhua quoted the Ministry of Water Resources as urging protection of the Zipingpu Reservoir between Dujiangyan and Wenchuan and said Dujiangyan would be "swamped" if major problems emerged at the dam.

Xinhua says the ministry set up an emergency command centre at the dam "to discharge the reservoir's rising waters and guarantee that the damage posed no threat to Dujiangyan and the neighbouring Chengdu Plain."

The dam was put into service in 2006, and international environmental activists had warned of the risk of earthquakes from nearby fault lines.

'Three Gorges Dam'

Sichuan has other major dam projects, including the massive Three Gorges Dam, the world's largest about 563km to the east of the epicentre.

The information office of State Council Three Gorges Construction Committee said earlier this week that there was no damage to the dam.

He Biao, the director of the Aba Disaster Relief headquarters in northern Sichuan, says there were also concerns over dams closer to the epicentre.

"The most dangerous problems are several reservoirs near Wenchuan," he said, according to a transcript on the CCTV Website.

He says problems at the Tulong Reservoir on the Min River could lead to collapse.

"If that happens, it would affect several power plants below and be extremely dangerous," he says.