Vietnamese police have detained 20 people involved in a protest outside the capital, Hanoi.

The dispute began Tuesday when hundreds of villagers clashed with as many as 3,000 riot police and other security forces. The villagers say the authorities were engaged in an illegal attempt to evict farmers from their land to make way for a new satellite city.

The villagers camped out Monday night in anticipation of the eviction, which was the culmination of a six-year land dispute in the Hung Yen district of Van Giang.

Officials say police used tear gas and fired warning shots to disperse the crowd, which was reportedly attacking police with rocks and bricks.

Land disputes have become increasingly common in Vietnam, a communist country where all land is owned by the state and usage rights are not always clearly defined.