Map of the earthquake's reach
The earthquake was felt as far away as Laos and Vietnam.
Rescue workers in China were still pulling survivors from the rubble Friday as they braved strong aftershocks and landslides days after a massive earthquake devastated parts of southwest Sichuan province.
The death toll from the magnitude-7.9 quake — the country's worst in decades — stood at more than 21,500, according to Sichuan Vice Gov. Li Chengyun. The government has said the toll is expected to exceed 50,000.
President Hu Jintao made his first tour of the disaster zone in Sichuan.
"The challenge is still severe, the task is still arduous and the time is pressing," Hu was quoted as saying by the official Xinhua News Agency. "We must make every effort, race against time and overcome all difficulties to achieve the final victory of the relief efforts."
A 5.9 magnitude aftershock rattled parts of central Sichuan on Friday afternoon, Xinhua said, citing its reporters at the scene. A number of vehicles were buried in landslides, and it was unclear whether there were casualties.
Experts say earthquake-aftermath studies show that the probability of finding survivors falls off dramatically after a critical three-day window.
Even so, people trapped for more than four days under tons of rubble were being pulled out alive. Rescuers freed a nurse trapped for 96 hours in the debris of a clinic in Beichuan county. Two other victims also were rescued in that area.
The first foreign rescue team in the disaster zone, from Japan, arrived early Friday. China initially had been reluctant to accept foreign aid, but the Foreign Ministry said Friday that specialist teams from Russia, South Korea and Singapore also were welcome.
Meanwhile, public anger was growing over accusations that shoddy construction, especially in schools, contributed to building collapses.
In a rare exchange with ordinary Chinese on a state-run Internet forum, the head of the Ministry of Education's development and planning department responded to initial reports on the number of destroyed schoolrooms — 6,898. Figures were still to come from the hardest-hit areas.
"If quality problems do exist in the school buildings, we will punish those responsible severely and give the public a satisfactory answer," said the official, Han Jin.
One school in Juyuan collapsed in seconds, killing all but a handful of the 900 students. In Mianzhu, close to where Hu arrived, seven fallen schools buried 1,700 people, Xinhua said. And about 1,300 bodies have been recovered so far.
An additional 700 students were thought to be buried under a crumbled school in Hanwang town. Farther north in Beichuan, about 700 students were buried.