Video footage captured the moments the protester and police clashed
Demonstrators in Gansu province, China, have attacked government buildings in protest at a plan to demolish homes, says state media.
Xinhua reported that thousands of people angry at having to relocate to make way for government developments used chains and axes to attack police.
Property and vehicles were damaged and several people injured, say reports.
Correspondents say that protests over land seizures have increased in China in recent years.
The Gansu protests were reported to have started after the local authorities announced plans to relocate the government of Longnan City, said Xinhua.
The move would force local residents to be resettled. Some homes had already been demolished when the protests began.
Protests first broke out on Monday and fired up 24 hours later.
"Protesters used iron rods, chains, axes, [and] hoes... to attack officials and policemen at close proximity," said a statement from the security forces.
They are also reported to have thrown stones, bricks and flowerpots at officials and police in front of the local government building.
Xinhua said 2,000 people had been involved in the unrest, but a local policeman told the AFP news agency that crowds had numbered several thousand.
"Yesterday the government brought in thousands of armed police who used tear gas and truncheons to disperse the crowds, and a lot of people were beaten," the policemen told the agency.
Video footage posted on YouTube appeared to show people throwing stones at men in uniform, who respond by hitting out with sticks.
One eyewitness told the Reuters news agency there were "a few thousand petitioners", a term used to describe people complaining to the authorities.
"Police fired tear gas which made women and children sick. This made the others angry," said the eyewitness, who did not give his name.
"We're not far from the government building, and although we closed our door, the smell of gas still came into our hotel. I heard a lot of people were hurt," another witness told AFP.
The authorities said the situation was under control by Wednesday after streets and junctions were closed.
Gansu province was severely damaged by the massive earthquake which hit neighbouring Sichuan in May 2008, which left some five million people homeless.
Commentators have suggested that the unrest could be linked to general discontent over the reconstruction projects and assistance given to those who lost their homes and belongings.
Many of those left homeless by the quake were reported to be still living in camps.
Gansu Communist Party chief Lu Hao said the rebuilding task was "extremely urgent" and that central government had approved the reconstruction plan for the areas.
Reporting a similar disturbance earlier this year, the BBC's James Reynolds, in Beijing, said that China has tried to address the issue of property seizure by passing a law giving ordinary people better protection against developers.
But people in many areas still feel that they are powerless to stop their land from being taken, he said.
Protests have also taken place against rising living costs and unemployment, and earlier this month hundreds of people rioted in the southern city of Shenzhen following the death of a motorcyclist close to a police checkpoint.