Special policemen armed with machine guns have begun patrolling the Beijing international airport while the subway passengers will face security checks from tomorrow as the Chinese capital tightened anti-terror drive for the Olympic Games in August.

At the airport, two-member teams of guards began work yesterday and would be based at all the three terminals through the Olympics beginning on August eight, state media reported, as the heightened security measures reflected China's concern for a trouble free and terror-free event.

"The special police will enforce the existing security force's capacity to deal with emergencies in the airport," a spokeswoman for the airport security bureau was quoted as saying by the state-run China Daily.

Wearing black uniform, the guards carrying machine guns became a point of attraction for passengers, as Chinese police are usually unarmed though some airport police carry pistols.

"I think they look cool, and you rarely get to see such big guns," the daily quoted a young woman as saying. But some others felt the presence of police armed with machine guns created an "unnecessary air of tension." Earlier reports said double fencing is being done around the airport complex and hi-tech devices installed to thwart possible terror attacks during the Games.

Beginning tomorrow, commuters will face security checks by machines, police or sniffer dogs at all subway stations in the Chinese capital, local authorities said.

Guns, ammunition, controlled knives, inflammables, explosives and radioactive and poisonous articles would be the focus of checks, a subway spokesman said, according to state-run Xinhua news agency.