An American religious foundation says the Chinese government has arrested a Roman Catholic bishop and four other members of an underground church group in the north of the country.

The Cardinal Kung Foundation said Han Dingxiang, the bishop of Yongnian in Hebei province, has already served about twenty years in prison.

Correspondents say Hebei province is a centre of China's unofficial churches -- known as house churches because ceremonies are held in private homes.

They say the arrests, which took place late last year, are part of a move by the authorities against people who ignore the government requirement that all Christians register in state-run churches. Earlier this month, relations between the Chinese government and the Vatican worsened when Beijing ordained five bishops, who had not approved by the Pope.

From the newsroom of the BBC World Service