Post-quake reconstruction in Sichuan province will take three years, vice-governor Li Chengyun said on Friday.

"The rebuilding efforts must overcome many challenges in the region, where mountains were shaken loose by the 8.0-magnitude quake and its more than 7,000 aftershocks," he told a State Council Information Office press conference.

"The priority will be finding proper locations for rural residents to build houses.

"We will strive to get houses ready for them before winter," Li said, adding infrastructure facilities were destroyed in eight mountainous counties.

He made the remarks on Friday afternoon, when the Information Office of the State Council said the death toll had reached 55,740, with 292,481 injured and 24,960 missing.

Li said the government's main concern is that aftershocks and heavy rain could cause secondary disasters, such as flashfloods and landslides.

He also said quake survivors need international assistance to cope with the emotional aftermath of the disaster.

"This quake has inflicted great psychological trauma on local residents and on orphans in particular," Li said. "We welcome and need help" from overseas psychiatrists and psychologists.

Wu Xiaoqing, vice-environment minister, said that 50 sources of hazardous radioactivity have been discovered so far in quake-affected areas. He did not elaborate on the total number of radioactive sources in these regions.

"The situation is under control, and there have been no signs of radioactive leaks," Wu said at another briefing.

"Thirty-five of the radiation sources have been recovered, and the locations of another 15 have been confirmed."

Three of the 15 sources were buried under rubble, while the other 12 were in buildings still too dangerous for technicians to enter, he said.

"We have asked the local government to inform us when they clean up the rubble."

Wu also said all nuclear facilities in Sichuan had undergone "careful monitoring and inspection".