MIANYANG, China - Chinese President Hu Jintao called here Friday for earthquake relief efforts to be stepped up, as he said rescue work had entered its "most crucial phase", state media reported.

"Quake relief work has entered into the most crucial phase," Hu said after flying into Mianyang, one of the worst-hit cities in Monday's massive quake that the government estimates killed at least 50,000 people.

"We must make every effort, race against time and overcome all difficulties to achieve the final victory of the relief efforts," the state-run Xinhua news agency quoted him as saying.

Hu met at the airport with Premier Wen Jiabao, who has been in the quake zone since Monday and has been portrayed by state media as intimately involved in directing disaster relief operations.

More than 8,000 people have died in Mianyang city alone in the 7.9-magnitude quake. Hu later set off for Beichuan, an even more devastated area.

Hu said that while saving lives was still the top priority, efforts should also be made to treat the injured and restore the infrastructure.

"The challenge is still severe, the task is still arduous and the time is pressing," Hu said.

Earlier Friday, Xinhua quoted Wen as saying the quake was the biggest natural disaster since the founding of the communist People's Republic of China in 1949.

He said it was even more devastating than the quake in the northern city of Tangshan in 1976 which claimed about 240,000 lives.

Although the toll from the Sichuan quake is not that high, the epic scale of it is becoming clearer -- and the number of dead is rising -- as teams move into the remote epicentre in Sichuan.

"It is still within the critical period for saving lives and we won't give up if there is even the slightest hope of finding more survivors," Wen said, according to Xinhua.

China has mounted a massive effort spearheaded by the military to reach devastated communities isolated by quake damage.

Xinhua quoted both Hu and Wen as describing the official relief work as "orderly, forceful and effective." - AFP/ir