HANOI (Reuters) - Thousands of riot police overwhelmed villagers in Vietnam who tried to block them from taking control of a disputed plot of land outside Hanoi on Tuesday in the second high-profile clash over property so far this year.

Villagers in the district of Van Giang just east of the capital had vowed to stand their ground after local authorities announced that they would forcibly appropriate 70 hectares (173 acres) of land for use in a satellite city development called Ecopark.

Many villagers camped out on the land overnight, burning bonfires and keeping vigil, photos showed.

But a force of 2,000-4,000 police and unidentified men not wearing uniforms converged on the land early on Tuesday morning, three villagers and one other witness said.

"We threw bottles of gasoline at them, but it did not help, they had shields. They used clubs to beat us. Even when we ran back to the village, they followed us and beat us," said a villager who gave his name as Kien.

As in China, where land grabs sparked a revolt in the southern village of Wukan that lasted for months, land conflicts are a leading source of friction between the public and officials in Vietnam. All land is owned by the state but usage rights are not always clear or protected.

Two people at the scene said they had heard what sounded like gunfire but Kien said the sound came from stun grenades that the security forces threw at the villagers. He said 10 people were arrested.

"They have acquired the land and used bulldozers to destroy our crops. We have lost to them. I don't know what to do next," he said.

A senior government official on the scene declined to comment and said to call back later. Officials at Viet Hung Urban Development and Investment Joint-Stock Co, which is developing Ecopark, could not be reached for an immediate comment.

Hung Yen farmers have been staging protests on and off since the Ecopark project was launched several years ago, claiming that the government granted land to the developers without proper consultation or compensation.

"If they want the land we just ask that the investors come to talk to us directly about it, but they won't," said a villager named Tuyen contacted by telephone in Van Giang.

At least two well-known, Hanoi-based bloggers rushed to Van Giang to chronicle the conflict. The issue has not appeared in state-run media.

In January, farmers outside the city of Haiphong ambushed security forces with homemade landmines and guns in a bid to stop local officials from taking their land.

The case was covered in state-controlled media and the fish farmer who organized the defense, Doan Van Vuon, was catapulted to cult hero status, piling pressure on the authorities over a highly sensitive issue.

In February, Vietnamese Prime Minister Nguyen Tan Dung publicly chastised local authorities for their handling of the case.

(Editing by Ed Lane)