Authorities re-arrested Father Thadeus Nguyen Van Ly, one of Vietnam's most outspoken dissidents, at a home for retired priests on July 25.

“We heard that at 2:30 p.m. police cars and an ambulance arrived at Nha Chung to arrest Priest Ly,” said Fr. Phan Van Loi in an interview with Radio Free Asia.

In March 2010, authorities granted the 63-year-old priest one year of medical leave from an eight-year sentence to seek treatment for a brain tumor, according to the Bangkok Post.

BBC News has reported that Fr. Ly's medical condition at the time of this week's arrest was unclear.

The priest is known for his peaceful protest of the communist state and its violations of human rights. He is a founding member of Bloc 8406 – the first well-organized pro-democracy group in his country, where many Catholics suffer because of communism.

In 2007 he stood trial for spreading anti-communist propaganda, and received a sentence of eight years in prison and five years of house arrest. The 2007 trial made headlines when Fr. Ly was forcibly muzzled after beginning to recite an anti-communist poem in court.

The government suspended Fr. Ly's prison sentence in 2009, following pressure from a group of 37 U.S. senators to release the priest after he suffered multiple strokes in jail.

The senators called Fr. Ly's trial “seriously flawed” in their 2009 letter, explaining that he was “denied access to counsel and precluded from presenting a defense” during the four-hour proceeding.

Fr. Ly has spent a combined total of more than 15 years in prison since 1977.

Although Vietnam's constitution provides for freedom of belief and religion, that constitutional right continues “to be subject to uneven interpretation and protection,” according to the U.S. State Department's 2010 International Religious Freedom Report.

Catholics account for seven percent of Vietnam's population. Along with other religious minorities, they have faced beatings, church raids, arrests and death for activities thought to challenge the authority of the government.

The question of property rights has been particularly contentious since 1975. In that year, the government began seizing Church properties, including schools and hospitals, and incorporating them into the state system. Although the government has returned some of the property, most ownership disputes remain unresolved.

In July 2009, Vietnam's government seized and demolished a Redemptorist monastery after ignoring years of petitions by the order. In May 2010, thousands of Catholics gathered to celebrate Mass on the site of a church that the government converted to a war memorial in 1996. Six Catholics were arrested in 2010 for protesting the government's development of a cemetery into an ecotourism resort.