BEIJING (AP) — Passengers riding the subway and major bus routes in Beijing will undergo strict security checks starting at the end of June ahead of the Olympics, police said today.

All subway lines and major bus stations will be equipped with security checkpoints, a spokesman for the Beijing Municipal Public Security Bureau Public Transportation Division said. Like many Chinese officials he gave only his surname, Chen.

High-traffic subway and bus stations will be equipped with police dog units and handheld metal detectors at each security checkpoint, the People's Daily, the mouthpiece of the ruling Communist Party, reported Friday. Explosives and flammable substances are already prohibited on subway lines.

Passengers will be checked for any liquids and will be asked to drink from any liquid containers they are carrying, the newspaper said.

With less than three months before the start of the Beijing games, China has launched a massive nationwide security campaign to head off possible protests, terror attacks and any sort of disorder that could challenge the government's image or tarnish its staging of the Olympics, a source of prestige and huge national pride.

In Beijing, the campaign has included increased security checks at hotels, entertainment areas and rented homes. Broader measures include visa restrictions that severely limit who can visit, live or work in China.

Large public gatherings are especially suspect, with police ordering the cancellation of several major events on security grounds, including a popular Beijing music festival this month.