Media playback is unsupported on your device Media caption The BBC's Jonathan Head in Burma: "It's become a test case for how old injustices will be addressed"

Police in Burma have used water cannon and tear gas to break up a protest against a vast Chinese-backed copper mine in the north-west of the country.

Protesters said dozens were injured and their camps set alight in Monywa town.

Local farmers, monks and activists have been protesting against what they say are forced evictions to allow for the expansion of the mine, Burma's largest.

Opposition leader Aung San Suu Kyi is in the area to meet protesters and says she wants to mediate a settlement.

Ms Suu Kyi was greeted by supporters who lined the streets.

Analysis When the government issued its ultimatum to the farmers and activists camped outside the Monywa copper mine, no-one could have guessed what would happen next. The rules have changed in post-military Burma, but no one is quite sure what they are. When I was there last Saturday the police guarding the mine entrance were shocked to see a solitary monk walking past the gate and its intimidating "Restricted Area" sign, towards them. One officer shouted at him to leave - the others resorted to holding hands, like children in a playground, in a line across the road. Eventually, the police relented and allowed a group of nuns to enter the site. It seemed then that we were witnessing a new era in Burma, one where violent repression was no longer an option for the security forces. Today we saw something of the old Burma, in the rough way the police broke up the farmers' sit-in, using water cannon and something else that seems to have set the protest camps alight. The government says it is still committed to a full inquiry into the farmers' complaint, that they were forced to accept the deal with the mining company under which they gave up their land for modest financial compensation and new but very basic housing. The Burmese parliament is now asserting itself, and there will surely be aspiring politicians there who will see backing the farmers' grievances against a Chinese- and military-backed mine as a vote-winner. This conflict is not over, and from what I saw and heard from the farmers, they will not give up their struggle easily. In pictures: Burma copper mine protest

"I already met one side. I met with mine operators. I want to meet with villagers and protesters," she said. "I want to negotiate after hearing from both sides."

The BBC's Jonathan Head, who recently visited the mine, says this is now being seen as a test case for how Burma's new government will handle growing protests around the country over land grabs that took place under military rule.

The farmers started their protest in June, saying they were forced to accept a deal two years ago under which they gave up their land in return for new housing and financial compensation.

The mine is owned by the military and Chinese arms manufacturer Norinco. The company has said that the deal was voluntary, and that only a small minority of farmers rejected it.

The mine's billion-dollar expansion project covers several thousand hectares of land in Burma's Sagaing region.

Squads of riot police arrived at the camps early in the morning, witnesses say.

"They shot some sort of canisters that caused fire at the camp. We just don't know what sort of weapon it was," Shin Oattama, a Buddhist monk, told Reuters news agency.

"We are now seeking refuge at a nearby village. There's no ambulance, no doctor to take care of the injured."

Of the 22 injured, many are monks, and they are mostly suffering from burns, our correspondent reports. It is not clear what caused the burns, he says.

President Thein Sein's office said in a statement that police had used water cannon, tear gas and smoke bombs to disperse the crowds. A spokesman denied that chemical weapons were used.

Laws on public protests in Burma have been relaxed amid a series of democratic reforms. But this week the government gave the protesters an ultimatum to leave the site.

Meanwhile, China has defended its joint mining project with Burma.

"The relocation, compensation, environmental protection and other issues involved with this project were jointly settled through negotiations by the Chinese and Myanmar [Burma] sides and meet Myanmar's laws and regulations," Foreign Ministry spokesman Hong Lei said during a regular press briefing in Beijing.

"We hope all levels of Myanmar society can provide an environment beneficial to the project's development."

In an editorial published on Thursday, the state-run Chinese newspaper Global Times said that halting the project would be a "lose-lose situation" for both countries.

"Only third parties, including some Western forces, will be glad to see this result," it said.