Local Catholics said the move was to prevent the new bishop from presiding over his first chrism Mass, a symbol of unity for the clergy.

"The security bureau informed the diocese that the provincial religious affairs bureau asked him to attend a learning class for 20 days," said a priest who asked not to be named, adding that has not heard of any other unregistered bishop in the province needing to do the course. China requires Catholic leaders to register with the government-controlled Catholic Patriotic Association, and Chinese authorities have frequently arrested Catholics who reject government control.

"Without the bishop, the chrism Mass is bound to fall through," the priest told ucanews.com, referring to the service that was planned for Holy Thursday, April 13.

Another church source condemned the authorities for creating confusion.

"How come they always make excuses to take the bishop away when a church feast needs his presence?" said the source.

According to church tradition, on the Thursday before Easter, all of the priests of a diocese gather with their bishop at the cathedral for the blessing of chrism and other holy oils used during the year. This year's chrism Mass would be Bishop Guo's first following the death of his predecessor, Bishop Vincent Huang Shoucheng, last July.

In Hebei province, where there are nearly 1 million Catholics, security officials took Coadjutor Bishop Cui Tai of Xuanhua from his sister's home around mid-February, two weeks after the Chinese New Year, ucanews.com reported.

"Bishop Cui has been under repeated detention since 2008 and is only allowed to come home from house arrest twice a year, for Chinese New Year and the moon festival," a Hebei church source told ucanews.com April 10.

"This is not due to leniency but because security officers also have to go home for the two festivals. After new year ends, the officials take him back again. He is now probably being detained in a hostel somewhere," the source added.