BEIJING, May 19 (Xinhua) -- China on Monday began a three-day national mourning for the tens of thousands of people killed in a powerful earthquake which struck the country's southwest on May 12.

At 4:58 a.m., the national flag at the Tian'anmen Square in downtown Beijing flew at half-mast after a complete flag-raising ceremony.

About 2,600 people watched the flag-raising ceremony in the square.

"I have been watching TV to know the disaster situation these days," said Yu Huilin, a 58-year-old retired teacher. Yu just arrived in Beijing by bus in the early hours on Monday from eastern Shandong Province.

"It's really heartrending," she said. "But I see the quake-affected people have got help from so many people. I believe they can recover from the disaster soon rebuild their homes."

All national flags will fly at half-mast at home and Chinese diplomatic missions abroad from Monday to Wednesday. Public recreational activities will be halted during the mourning period.

At 2:28 p.m. Monday, Chinese citizens nationwide will stand in silence for three minutes to mourn for the victims, while air raid sirens and horns of automobiles, trains and ships will wail in grief.

In the mourning period, condolence books will be opened in China's Foreign Ministry and Chinese embassies and consulates around the world.

The Beijing Olympic torch relay will also be suspended from Monday to Wednesday.

The death toll from the massive quake rose to 32,476 nationwide as of 2 p.m. Sunday, while the injured numbered 220,109, according to the emergency response office under the State Council.

Among the dead, 31,978 were in Sichuan alone with the rest in six other provinces and a municipality.

The quake hit Wenchuan County, Sichuan Province, at 2:28 p.m. of May 12. Many other areas were also affected.

The search, rescue and disaster relief efforts are continuing. Some 113,080 Chinese soldiers and armed police have been mobilized to help with rescue operations. Rescue teams from Russia, the Republic of Korea, Japan and Singapore, as well as Taiwan and Hong Kong regions, have also joined in relief efforts.