Chinese authorities have arrested a Roman Catholic priest as part of a continued crackdown on churches and other groups that are not sanctioned by the state.

Religious rights advocates in the United States first revealed that Roman Catholic priest Zhao Kexun, believed to be in his mid 70s, was detained by security agents in northern China's Hebei province this week.

He is among the more than 30 priests and other religious practitioners who have been imprisoned in the province recently, as authorities crack down on churches that operate outside the state's supervision.

At a briefing Thursday, Foreign Ministry spokesman Liu Jianchao restated the government's policy of not tolerating worship in churches that are not sanctioned by the state.

"In China, any social community should register with relevant civil administration departments, and religious groups are no exception," he said.

The Chinese government says there are four million Catholics in China, but Western academics estimate the figure is closer to 12 million. Officially, they are limited to worshipping in churches that are not considered to be under the authority of the pope in Rome.

Chinese Communist authorities forbid any expression of allegiance to the Vatican, which remains locked in a dispute with Beijing over China's continued refusal to let the Pope appoint Chinese bishops.

During her recent visit to Beijing, U.S. Secretary of State Condoleezza Rice emphasized the Bush administration's calls for China to expand religious freedom.

The priest's arrest this week comes as international advocates call attention to what they say is a growing crackdown on pro-democracy intellectuals and freedom of expression in China.

The Reporters Without Borders media advocacy group on Wednesday condemned the removal of Beijing University journalism professor Jiao Guobiao from his post. He angered officials by publishing a pamphlet saying the Communist Party's policies of censorship are stifling the growth of Chinese society.