Vatican City - The Vatican on Thursday said it felt "deep pain" over the re-arrest in China this week of an elderly Roman Catholic bishop from the country's "underground" church which remains loyal to the pope.

Police on Monday arrested Bishop Julius Jia Zhiguo of Zhengding, a county in China's Hebei Province some 260 kilometres south of the capital Beijing, Catholic media reported.

The 74-year-old Zhiguo has spent some 20 years in prison and has reportedly been taken into custody a dozen times since 2004.

The latest arrest "unfortunately is not an isolated case," the Vatican statement said.

"Other clerics are also deprived of their freedom and subject to undue pressures and limitations in their pastoral activities," it added.

Monday's arrest came as a Vatican commission began meeting in Rome to review conditions faced by Catholics on mainland China.

China's estimated 13 million Catholics are spilt between the state-sanctioned Patriotic Catholic Association and the underground church.

The commission, whose meeting ended on Wednesday, in its discussions also drew upon participants' "own sometimes-harsh experiences," the Vatican said.

It "highlighted complex problems of the current ecclesial situation in China, problems deriving not just from internal difficulties of the Church, but also from the uneasy relations with the civil authorities," the Vatican statement said.

The Vatican does not have diplomatic relations with China, whose officially atheist government cut ties in the early 1950s.

Benedict was seen to break new ground in relations with Beijing when in June 2007 he sent a letter to Chinese Catholics expressing admiration for the Chinese people, but also the need for greater religious freedom in China.