Security for the nation's 60th anniversary celebrations is set to be tighter than during the Beijing Olympics with a massive anti-terrorism drill launched yesterday in regions around the capital.

Anti-terror drills combating mock attacks from low-grade nuclear weapons and toxic chemicals as well as simulated hijackings and street shooting, are expected to cost millions of yuan and involve thousands of SWAT police and soldiers.

Security experts said the scale of the operations shows that the security level for the Oct 1 event will be even higher than the Games last summer.

The unprecedented measures follow a series of suspected terrorist attacks and incidents around the nation.

Major cities have recently raised their security alerts in the wake of a bus fire last Friday in Chengdu, which claimed 27 lives and injured dozens. Police have not ruled out terrorist involvement in the incident.

In neighboring Chongqing, security forces are hunting for a man who killed a soldier before snatching his gun in March.

Threats to the capital and neighboring regions have been growing, and terror organizations and separatist groups, such as the East Turkistan Islamic Movement, have warned of attacks, anti-terror specialists said.

The potential targets appear to be politically-sensitive sites, rather than venues of international interest targeted during the Olympics, said Li Wei, director of the Counter-Terrorism Studies Center at the China Institutes of Contemporary International Relations.

"But their ambition of hitting high-profile targets has not diminished," he said.

Bomb specialists, armed forces and medical teams were sent to the site of a "dirty bomb" explosion yesterday in Inner Mongolia's Hohhot.