BEIJING, July 29  -- Beijing has stepped up security checks at public transport stations to fight terrorism and safeguard stability during the summer vacation, local police announced Tuesday.

Passengers and liquids will be checked at subway stations, said Tan Quan, deputy head of the traffic corps of Beijing's Municipal Public Security Bureau.

According to the new measure, the number of security personnel at each subway checkpoint will increase to four or five. This is usually the standard during rush hour.

Tan said managers of security companies should also be present to monitor operations. Armed police will be dispatched to key subway stations, and garbage bins in stations will be checked every 15 to 20 minutes.

The new measure previously applied only to very important events, like the annual sessions of the National People's Congress and the Chinese People's Political Consultative Conference, Tan said.

As for buses, police will ask bus companies to deploy safety supervisors to check passengers at stations and on buses.

Meanwhile, passengers who reject security checks will be detained by police. This year, more than 120 passengers have been detained for taking dangerous items to subway stations, while over 30 have been punished for rejecting security checks.

With visitors traveling to Beijing during the summer vacation, more police officers will be patrolling crowded places, especially subways, said Tan.

Beijing is home to 21 million permanent residents. The city has 465 km of subway lines in operation, which carry 10 million passengers daily.