The death toll from the country's worst earthquake in three decades is estimated at more than 50,000, the rescue headquarters of the State Council said on Thursday, as rescuers finished rushed repairs on a quake-damaged road from Lixian county to the epicenter at 9 pm.

The figure was a sharp rise from 20,000 confirmed deaths reported earlier from Monday's 7.8-magnitude quake.

Sichuan Vice-Governor Li Chengyun told a press conference that another 102,000 people were injured.

Rescuers have been struggling to reach all quake-hit areas, battling landslides, buckled roads, collapsed bridges and wet weather.

As of 8 am on Thursday, more than 130,000 troops were engaged in rescue operations in areas ravaged by the quake - and they had reached all 58 counties and towns stricken by the massive quake.

The newly opened road - part of a national highway from Nagqu in Tibet to Chengdu - ensures faster delivery of disaster relief materials to the epicenter of Wenchuan, the first time after it was blocked by landslides when the quake struck on Monday.

Premier Wen Jiabao went to Qingchuan county on Thursday, near the badly-hit Beichuan county, by boat to oversee rescue work.

He told disaster relief personnel including firemen and medics that "the Party and the country thank you and the people need you".

An aerial view of a town in the epicenter of Wenchuan County, Southwest China's Sichuan Province, after the deadly May 12 earthquake, in May 14, 2008. [Xinhua]

Wen encouraged residents to "rise from sorrow, help each other and rebuild homes".

He said that government will make the utmost efforts to help the victims. "See, a large number of soldiers are coming. Food, water and tents will also come soon."

Experts said the rescue window was getting smaller.

"Within 72 hours after the disaster is the critical period. Generally, the sooner the victims are rescued, the better," Liang Guiping, the chief engineer of Shijiazhuang Bureau of Seismology, told CCTV.

Wang Zhenyao, director of the disaster relief department of the Ministry of Civil Affairs, told a press conference on Tuesday that transportation hurdles and the huge number of victims were the two major difficulties facing rescue and relief workers.

Meanwhile, huge amounts of relief materials are required, Wang said, adding that up to 60,000 tents are needed in Mianyang alone, putting further pressure on transport.

Still, there was encouraging news from many sites: After being trapped more than three days under debris, a 22-year-old woman was pulled to safety in Dujiangyan.

A soldier gives a wounded woman water at the earthquake-hit Beichuan County, about 160 kilometers northeast of the epicenter of Wenchuan County, Sichuan Province, May 13, 2008. China dispatched more soldiers to the earthquake-ravaged province of Sichuan on Wednesday to quicken a search for survivors. [Agencies]

Covered in dust and peering out through a small opening, she was shown waving on CCTV shortly before being rescued.

"I was confident that you were coming to rescue me. I'm alive. I'm so happy," the unnamed woman said on CCTV.

Secondary disasters

Minister of Water Resources Chen Lei said on Thursday that damaged water infrastructure, including reservoirs and hydropower plants, poses a threat to flood control and security in quake-stricken regions.

This Sept. 14, 2007 picture released by GeoEye Satellite Image shows the Zipingpu Dam, upriver from the town of Dujiangyan, Sichuan, China. [Agencies]

Chen, who is also head of the ministry's command center for disaster rescue and relief operations, said Sichuan had a large number of reservoirs, many of which had sustained significant damage during the quake.

The National Development Reform Commission said the earthquake had damaged 391 dams. It said two of the dams were large ones, 28 were medium-sized and the rest were small ones.

More than 2,000 troops were sent to work on the Zipingpu dam, which lies on about 6 miles up the Minjiang river from the badly damaged city of Dujiangyan.

Also unknown was the extent of damage to hydropower plants owing to inadequate management systems and poor data collection, he said.

It is crucial to prevent secondary disasters, and control floods at damaged reservoirs, hydropower plants and dikes, he stressed.

He noted that it is necessary to study and judge potential dangers at these facilities by analyzing satellite and other aerial images.

Earlier in the day, the Water Resources Ministry said the Zipingpu dam, near the quake epicenter in Wenchuan, is structurally stable and safe.

But the multi-functional facility sustained some damage during the quake, including cracks at the top and collapsed workshops, according to the emergency response office of the Sichuan provincial government.

Other developments:

Public security departments have punished 17 rumor mongers in the wake of the earthquake, the Ministry of Public Security said on Thursday.

The ministry did not mention what exactly the rumors were, but claimed that the culprits "spread false information, made sensational statements and sapped public confidence".

Power has been restored in most parts of Sichuan, the State Grid Corporation of China announced on Thursday. However, people in Beichuan county and Aba prefecture were still suffering a blackout.

A Japanese rescue team is expected to arrive in Sichuan today. The rescue team, comprising about 60 members, will be the first foreign disaster relief professionals to assist China since the quake struck on Monday.

Editor: Yan