Yang, who is nearly 81, has served a total of 30 years in prison, the Kung Foundation said.
He was imprisoned from 1955 to 1981 for refusing to denounce the pope's authority as head of the Catholic Church. In the 1950s the Chinese government under Mao Zedung forced all Catholics to join the government-controlled Catholic Patriotic Association, which rejects ties to the Vatican.
Membership in the Catholic Patriotic Association is about 4 million, but Western researchers say that another 8 million are members of the unregistered Catholic Church.
Archbishop Yang was incarcerated again for another three years in 1988 and has been arrested many times since then.The immediate cause of his latest arrest was not reported.
Joseph Kung, president of the Kung Foundation, says that China is holding "scores of priests and lay persons " and at least eight underground bishops in prison, including An Shuxin, Han Dingxiang, Jia Zhiguo, Lin Xili, Su Zhimin, Xie Shiguang, Yang Shudao, and Zhang Weizhu.
Han Dingxiang, the bishop of Yong Nian, was arrested on or about Dec. 1 while leading a religious retreat in Shijiazhuang, the capital of Hebei Province in central China. The 63-year-old Han is being held at an unknown location, the Kung Foundation reported in January.
China is waging a campaign to "eradicate the illegal activities of the underground Catholic Church," according to a secret government document published by the Kung Foundation in 1997. According to the Catholic news service Fides, a more recent document, dated Aug. 17, 1999, stated that the government's plan that the underground Catholic Church "be eliminated by re-education, forced labor, dismissal, and isolation of stubborn priests, and bishops" is being carried out in earnest.
Kung urged nations with influence to take into account China's prisoners of conscience as it seeks to enter the World Trade Organization. "The persecution of underground Roman Catholic continues and is escalating even (as) China has achieved impressive economic progress," he said.
In recent months, the Beijing government, seeking to maintain its firm control over the Chinese population, has cracked down on a variety of religious groups. In addition to the underground Catholic Church, underground Protestant churches, the Falun Gong movement and other such groups have seen members arrested.