A Tibetan school teacher, believed to be China's longest-held political prisoner, has arrived in the United States after being released from prison for medical reasons.

Seventy-four-year-old Tanag Jigme Zangpo arrived in Chicago on a flight from Beijing Saturday. He was released from Drapchi prison in the Tibetan capital, Lhasa, on March 31, on medical parole, nine years before the end of his sentence. He had spent more than three decades in Chinese jails and is said to be suffering from heart disease and high blood pressure.

The United States welcomed the news. State Department spokeswoman Brenda Greenberg said the release came after the active involvement of U.S. officials as well as non-governmental organizations.

According to a London-based group called the Tibet Information Network, Mr. Jigme Zangpo, a primary school teacher, was first sentenced to three years of "re-education through labor" in 1965 for political activities. He is also said to have served a 10-year sentence starting in 1970.

In September of 1983, he was convicted once again for campaigning against Chinese rule in Tibet and sentenced to 15 years in prison. His sentence was extended twice while he was in prison and was due to expire in September of 2011.