"We need to pray for these bishops and priests ... but we must also appeal to those who are holding" them, Archbishop Hon said, endorsing a public campaign recently launched by AsiaNews.

Eight of the arrested clergy are members of the so-called "underground" or clandestine Catholic community, whose leaders refuse to register with the Chinese government.

The government's refusal to acknowledge the church leaders' detention shows that the priests and bishops "disappeared for religious reasons," Archbishop Hon said. "If these people have done something wrong, please send them to court, not to prison or isolation."

Asked what the Vatican is doing to obtain their release, Archbishop Hon said that requests were being made through personal channels and diplomats from third countries. But he also noted that the "Holy See cannot publicize all the help it gives and its closeness to them."

Noting that the Vatican does not distinguish between Catholic communities that register or do not register with the government, the archbishop called for unity of the church in China in spite of government persecution.

"It is also important that the underground communities learn to forgive," he said. "The martyr, like St. Stephen, is also one who forgives."

China requires bishops to register with the government, but many refuse, believing registration forces them to operate within certain limits. Those who, for decades, refused to register and suffered persecution at the hands of communist authorities have sometimes felt resentment toward those who opted to register and cooperate; initially they were forced to keep their loyalty to the Vatican secret.

A 2007 letter from Pope Benedict to Chinese Catholics "leaves the decision to the individual bishop," having consulted his priests, "to weigh ... and to evaluate the possible consequences" of registering with the government.