Thousands of residents protested in a southeastern Chinese city after a traffic accident, smashing police cars and overturning three police vans, police and residents said.

The reason for the protest in Fuan city in Fujian province was unclear. Police said it was instigated by "a handful of lawless people." One resident said people became angry because police and paramedics took nearly an hour to arrive to help the injured, while a Hong Kong-based human rights group said it was to do with corruption.

But such protests have become increasingly common in China, and Saturday's violence is another reminder that the country's new leadership has to deal with underlying social discontent that often boils over. People are fed up with corruption and high-handed officialdom, pensions that have not kept pace with inflation, and families being forced from their homes to make way for developments.

Residents said police were stopping cars and checking people for driving after drinking on Saturday evening when the accident happened on a main road in Fuan.

Wanting to avoid being tested, a driver in a sedan accelerated away and police started chasing the car, said a resident, who would give only his surname, Lin. About three motorcycles were hit during the chase, said Lin, adding he wasn't sure who hit them.

"About 10,000 to 20,000 onlookers became angry because police officers and paramedics took nearly one hour to arrive," said Lin.

He estimated that 1,000 to 2,000 people clashed with police and overturned three police vans.

Photos carried by online southeastern news sites showed hundreds of people swarming across a wide street with two vans thrown onto their sides. In one photo, three people stood on top of an overturned van.

The official Fuan city police microblog said Sunday that a sedan had collided with a car and three motorcycles just before 8 p.m. Saturday, leaving five people injured.

"The accident made a small number of local people dissatisfied, so they smashed police vehicles and overturned three police vans," said the statement.

An initial investigation found that a person with no driving license surnamed Jiang had caused the accident and was in police detention, it said. It said the driver wasn't drunk but had accelerated to avoid a patrol vehicle and aroused attention.

It said four of the injured were in stable condition and the other one had been discharged from hospital.

Later Sunday, the propaganda department of Fuan's Communist Party committee put out a statement countering accusations police and paramedics had been slow to respond.

It said police had immediately called paramedics and traffic police after the collisions, and a patrol car drove to a hospital to pick up three doctors. The five injured were taken to hospital 40 minutes after the accident happened, it said.

"As the rescue work was going on, some relatives of the injured people and onlookers got out of control," said the statement. "They started to push and shove the doctors and knock the ambulance and so the ambulance left the scene under police escort."

It said "a handful of lawless people misled some people who didn't know the truth" and they began targeting police vehicles.

The Hong Kong-based Information Center for Human Rights and Democracy said about 10,000 people clashed with police, and that 10 police vehicles had been smashed, three overturned and 20 people injured.

The scenes were triggered by the local police corruption, the center said in a faxed statement that didn't cite any sources.

It alleged that Fuan's traffic police were illegally registering license plates to vehicles from outside their jurisdiction for 50,000 yuan ($8,000) and that local residents suspected the sedan had such a license.

Calls to Fuan's transport bureau rang unanswered. A man at Fuan's local government propaganda department didn't answer questions but referred to a press release on a local news portal which said the same as the Fuan police microblog.