Retired Cardinal Joseph Zen Ze-kiun of Hong Kong told ucanews.com that the government was tightening religious rules, with one source telling him there would be no Mass in a Shanghai underground church.
"The priest has told Catholics not to come because there will be no Mass since they have not registered," Cardinal Zen said.
A priest in Hebei province who asked to be anonymous told ucanews.com that authorities had asked clergymen in some parts of the province to post signs prohibiting minors from entering religious venues, prayer houses and other church premises.
"They also threaten churches that they cannot be used if they refuse to post the signs," he said.
A blogger wrote that "religious venues are the third premises following clubs and internet bars where minors are prohibited from entering by authorities."
Peter, a Catholic in central China, said he had seen such signs posted in churches in Xinjiang.
He told ucanews.com there are no legal grounds for officials prohibiting minors from entering religious venues. He accused officials of violating China's constitution, the communist-run country's supposed highest law.
"When minors enter internet bars, the government and police turn a blind eye. However, they are becoming very strict in prohibiting minors from entering religious venues. It is ridiculous," he said.
Peter said the constitution clearly stipulates that citizens have religious freedom, while protection laws state that teenagers and children cannot be discriminated against because of their religious beliefs.
Fr Stephen of the underground church said children in school have to tell lies to cover their faith and not to express their true feelings. "Is this the way to build up our civilisation?" he asked.
Before the regulations, communist authorities were already tightening their grip on practicing Christians. Last August, ucanews.com reported at least four regional governments had issued notices that restricted children from joining Christian groups and attending religious activities.