Rev Phan Van Loi told Radio Free Asia that local police have been monitoring his movements in the city of Hue since January.
"I asked them why they were blocking me from attending church services," he said. "I asked if they were police. Of course, I knew they were police because I had previously seen them around my house."
- Population: 95.4 million (8.4 million Christians)
- Main Religion: Buddhism
- Government: Communist state
- World Watch List Rank: 17
- Source of Persecution: Communist oppression/ Ethnic antagonism
- According to Open Doors, 35 churches were attacked in 2016
Rev Loi believes he is subject to investigation because he had been in contact with people at the Thien An monastery, whose property has been subject to land grabs.
In 2015, the government had tried to seize monastery land in order to build a leisure centre. The following year, authorities claimed that priests had erected a cross on government land next to the property and took it down as the priests were praying around it.
It is one of a number of recent cases in which the government has laid a claim to church property.
Vietnam, a Buddhist-majority country, is number 17 on Open Door's World Watch List 2017 for Christian persecution.