Nearly 100 members of China's underground Catholic church clashed with police in the north of the country this week demanding the release of an arrested bishop and priest, a US-based human rights group said.

About 500 police attacked the group in Zhangbei county in Heibei province on Wednesday morning when they demanded the "immediate release" of 82-year-old Bishop Yao Liang and Father Li Huisheng, the Cardinal Kung Foundation said.

It did not say why they had been arrested. About 90 Catholics were arrested during the clashes with the police, during which two men were injured and a pregnant woman had a miscarriage, it said in a statement received by Reuters yesterday.

A government official reached by telephone said that the Catholics had caused "chaos" but denied there had been a clash between them and the police.

"The Catholics were deliberately provocative," he said, declining to provide his name.

"It is just a rumour that the police fought with them. In fact, it was a dispute between two different groups of Catholics," he said without elaborating.

The official also denied there had been any arrests or injuries.

China's ruling Communist Party is atheist but tolerates religions that accept official supervision, and oversees state sponsored groups of Christians, Muslims and others.