Vietnamese authorities have taken one of the country's most prominent dissidents back into custody, more than a year after he was granted medical leave.

State media say Nguyen Van Ly — a Catholic priest — was re-arrested Monday because he continued anti-government activities. The reports said these included calling on people to protest China's activities in waters Vietnam claims, and criticizing the government's response to the territorial dispute.

Ly has been a long-time critic of Vietnam's communist government, and has called for freedom of speech and democracy. He has spent more than a decade in prison. He was freed in 2005, then arrested again in 2007 and sentenced to eight years in prison. In 2010, he was freed for one year for health reasons. Authorities did not return him to prison in March when the year was up.

The United States and human rights groups have urged the Vietnamese government to free Ly.