Bishop Julius Jia Zhiguo of the underground Church's Diocese of Zheng Ding was released Friday after five days of detention, a U.S.-based watchdog group said.
Joseph Kung, president of the Connecticut-based Cardinal Kung Foundation, said the prelate had been arrested June 13 by two policemen in Hebei province in northeast China along with Trappist Father Placid Pei Ronggui.
Kung gave no details about the release, and there was no word on the bishop's whereabouts. The priest had been released earlier, but details weren't available.
Bishop Jia Zhiguo heads one of the most active dioceses in the province, which has about 1.5 million Catholics.
The 69-year-old bishop has lived almost all his episcopal ministry under house arrest. Authorities arrested him last April but allowed him to celebrate Mass. He was also detailed in March 2003 and in March 2002, a few days before Holy Week.
Following the bishop's arrest last April, the Holy See described his detention as inadmissible in a state of law.