The two monks, Dang Thanh Dinh, 42 and Dang Van Nghia, 38, allegedly carried out religious services, offered unregulated medical check-ups, and distributed CDs and cassettes containing "private religious missionary content."
On Monday, Vietnamese authorities organized a press briefing in Can Tho to publicize alleged violations by Dinh and Nghia.
Authorities said the two monks and their followers "held gatherings without permission on the seventh and eighth days of every month." They described the monks as "opinionated and extremist," the official Viet Nam News reported Tuesday.
Hop said the government would dismantle places of worship built illegally. If the monks continue to organize religious services without permission, Hop said, the government will "take strong measures" against them.
Hoa Hao is an indigenous Buddhist sect founded in 1939 by the Vietnamese sage Huynh Phu So. It has up to 2 million followers concentrated in the Mekong Delta area, and was officially recognized by the government in 1999.
Under Vietnamese law, all religions are required to register for approval with the government's Bureau of Religious Affairs.