BEIJING -- An angry crowd of about 2,000 rioted in northwest China's Gansu province over a government plan to demolish a downtown area, torching cars and attacking a local Communist Party office, injuring 60 officials, state-run media reported yesterday.

The violence, one of the most marked instances of social unrest to grip China in recent months, was sparked by government plans to relocate the city of Longnan's administrative center after May's devastating earthquake, according to the Xinhua news agency.

At one point, rioters met a surging wall of armed police officers with a hail of rocks, bricks, bottles and flowerpots. The crowd later confronted police with iron bars, axes and hoes as they tried to hijack a fire truck and smashed windows and office equipment in two government buildings.

State-run press has reported on numerous pickets and demonstrations that have broken out across China in recent weeks, including a two-day strike by disgruntled taxi drivers in the southwestern Chinese city of Chongqing. Activists warn that tensions over the sudden downturn in the Chinese economy could provoke similar public outbursts, even though police have made efforts not to resort to violence immediately in quelling the riots.

Chinese economists say rising wages throughout China have led many laborers to expect better working conditions and residents to demand more accountable government.

"The local government has become the front line of conflict," said Hu Xingdou, a Beijing Institute of Technology economics professor. "But there is no channel to allow people to express their will. They lack the right to speak, the right to organize and unionize to represent their interest; therefore, they can only use an irrational way, by demonstrating or rioting to solve problems."

But government officials recently began to forego a decades-old policy of meeting public demonstrations with swift repression. Following a two-day strike, Chongqing taxi drivers were able to air their grievances in a three-hour meeting with government officials that was available online across China.

The Longnan melee began as about 30 angry residents gathered Monday outside the party office, but the crowd soon grew much larger, Xinhua reported.

He Zhouwa, manager of a local machine brick factory, said people were ready to use any means possible to stop the government plan to relocate the city center. "People are still at the municipal party office compound," he said late yesterday. "I did not dare to go there, but everyone is talking about this. There were hundreds of petitioners there last night and this morning."

The Longnan city government said in a statement on its Web site that the crowd -- many of whom had come to petition government officials over the loss of their homes and land to the relocation plan -- was "incited by a few people with ulterior motives."