The confrontation started Monday when about 150 Catholics built the structure intended for religious services on the site of the Tam Toa church, which was destroyed by U.S. planes in 1968, Father Pham Dinh Phung said Wednesday by telephone from Quang Binh province, the Associated Press reported.
"The police beat the Catholics, and some of them were bleeding," Phung said, adding that officers dismantled the makeshift church and took away the cross.
The communist newspaper Ho Chi Minh City Law however gave a different version of the story, it says, "The incident flared on Monday when police stopped residents from reconstructing a building on the foundation of the bombed out Tam Toa Church."
"Functional organs explained (the situation), encouraged people to dismantle the house and suspend construction of the altar because such work is illegal," said the newspaper, which is run by the city's justice department.
It said a fight then started with some "extremists" shouting and inciting others to throw bricks and stones at the police, injuring two officers.
A letter on the Web site of the Vinh diocese, where the church is located, from Le Thanh Hong, a priest from the Tam Toa parish, said "no less than 20" people had been detained.
The provincial government had turned the Tam Toa church site into a Vietnam War memorial in 1991. Catholics have since been forced to hold religious services at a house nearby but have pushed for a new church, Father Phung said.
"Church leaders met with provincial government officials about a year ago and they promised to give us land, but so far they haven't kept their words," he told AP.
Tran Cong Thuat, deputy governor of Quang Binh told AP that the local government has recommended five places for the site of the new church, but Catholic leaders have not agreed on any.
Meanwhile, police released two 15-year-old girls but others remained jailed, Father Phung said. "We strongly protest the beating and arrests of the Catholics and demand their immediate release."
After taking power from the French in 1954 in what was then North Vietnam, the communist government confiscated much of the Church's property.
Vietnam with over 6 million Catholics is home to the second biggest Catholic population in Southeast Asia after the Philippines. Hanoi does not have diplomatic relations with the Vatican.
Open Doors, a Christian ministry monitoring and defending persecuted Christians around the world in its Open Doors Watch List 2009 has placed Vietnam 23rd spot under 'Severe Limitations' category along with countries like China, Pakistan, Myanmar (Burma), Iraq and others where Christians cannot practice their faith freely.