BEIJING — Explosions on two public buses in southwest China early Monday killed two people and wounded 14, heightening fears of terrorism just weeks before the opening of the Olympic Games.

The separate blasts went off in downtown Kunming city in southwest Yunnan province, the Yunnan Public Security Bureau said in a notice on its Web site. They were deliberately set, it said. Photos on the Internet showed a bus with all its windows shattered and a gaping hole in its side.

The official Xinhua News Agency said a destroyed bus was seen in front of the Panjiawan bus stop, and broken glass was scattered in front.

The government has boosted national security to ensure a worry-free Olympics they say are a target for terrorism. Checks at subway stations and airports have increased, and anti-terrorist forces are being deployed to Olympic sites.

Police closed roads and set up checkpoints to prevent suspects from escaping, the police report said.

The first explosion occurred at 7:05 a.m. on public bus 54 on West Renmin road, and the second at 8:10 a.m. at a nearby intersection, the report said.

No further information was available. The Kunming police refused to comment, saying the information had been released in Xinhua reports.

Local officials throughout China have been told to avoid mass incidents or any signs of unrest before the games begin. But rural protests have been on the rise in China, becoming a way to air grievances and anger at local governments.

Last month, 30,000 rioters set fire to a police station and police cars in a small town in hilly Guizhou province, angry over an alleged cover-up of a local teenage girl's death.

Also Monday, the state-run China Daily newspaper cited the Olympics security chief Ma Zhenchuan as saying that a radical Islamic group based in China's predominantly Muslim Xinjiang region "poses a real threat to the Beijing Olympics."

Ma said investigations have found that the East Turkestan Islamic Movement, or ETIM, has been plotting terror attacks on games venues. "It's not imaginary," he was quoted as saying in the English-language daily.

Radicals among Xinjiang's indigenous Turkic Uighur people have been fighting Chinese rule for decades. Earlier this month, Chinese authorities said they had detained 82 suspected Islamic terrorists and separatists in the first half of the year across Xinjiang.

Most experts say the actual threat to the Beijing Games from terrorism is low, although the event has become a magnet for critics of the government, ranging from free-speech advocates to activists over Tibet and Sudan's troubled Darfur region. China has prepared an anti-terror force of nearly 100,000 commandos, police and troops for the Olympics.