Authorities in northern Vietnam have detained 20 people after thousands of police evicted farmers from their land to make way for a satellite city, witnesses and state media said Wednesday.

More than 1,000 villagers were overpowered by some 3,000 police and militiamen, many of them in full riot gear, during Tuesday's incident, said a protester who gave her name only as Thinh.

She said villagers had camped out at their farms overnight to try to hold onto their land. Police fired tear gas and smoke grenades to disperse the farmers, who pelted them with rocks and bricks.

A video posted on YouTube showed police beating a villager. The sound of shots can be heard in the background. The video could not be verified, and it was unclear who was firing the shots and what type of weapon was being used.

Wednesday's Thanh Nien newspaper quoted Bui Huy Thanh, chief administrator of Hung Yen provincial People's Committee, as saying police detained 20 villagers for their "extremist behavior," seized gasoline bottles and many bags of bricks, and are investigating ring leaders for assaulting officials on duty.

"This group of people do not have any other demand than demanding to cancel the project and return land to the villagers," he said. "This demand is unacceptable because the project was approved by the prime minister ... and people's interests were met fairly."

Thanh said the eviction involved 5.8 hectares (14 acres) of 166 families, part of the 72.6 hectares (180 acres) in the second phase of the project.

The Ecopark project was awarded to Viet Hung Co. Ltd., a private company, in 2004 to develop a satellite city in Hung Yen province that would cover 500 hectares (1,235 acres) in three villages about 20 kilometers (12 miles) southeast of the capital, Hanoi, officials have said. More than 4,000 families will lose their farmland.

The farmers had periodically staged protests in Hanoi to demand higher compensation or cancel the project altogether.

Another protester who gave her name only as Kiem said her family lost 900 square meters (9,687 square feet) of land as a result of Tuesday's eviction.

Kiem said the company initially offered 55,000 dong ($2.70) per square meter of farmland in 2005 and has since raised the rate to 150,000 dong ($7.50). However, her families and some 1,800 others did not agree to give up their land.

"We are farmers, we need land to make our living," she said by telephone from Hung Yen. "Now that we lost our land, how can we survive?"

The incident comes after another high-profile land dispute this year involving a fish farmer in the northern port city of Hai Phong who allegedly attacked authorities with homemade land mines and improvised shotguns as they were moving in to evict his family.

The case has attracted so much attention that Prime Minister Nguyen Tan Dung demanded an investigation, ruling in February that the eviction was illegal and that those who ordered it should be punished. He also encouraged local authorities to renew the family's land lease.