The profiles show prisoners' pictures of themselves drinking tea together at night or showing off tattoos, messages between inmates, and status updates such as "taking drugs in prison.
"That post, on an account under the name of Nguyen Duc Hung, attracted 6 "likes," according to a screenshot published Friday by newspaper Dan Tri.
A page in the name of Sat Thu Tran showed the inmate's chat with his girlfriend, who said he should stay in prison forever as life seemed so good inside.
"It is unacceptable that prisoners can live in such a way in prison," a Dan Tri reader commented online. "Those convicts will continue to commit crime after leaving prison because living there is pleasure."
"What the hell are police officials doing in this prison?" wrote another.
Wardens caught Nguyen Duc Hung using a smartphone in breach of rules at Tan Lap prison, 80 kilometres north-west of Hanoi, Dan Tri newspaper reported, quoting an unnamed police official.
Hung had been punished before for chatting with his wife online.
"I don't know why these Facebook pages still showed photos of prisoners on Wednesday," a prison official told dpa by phone, asking not to be named. "The two Facebook accounts were closed Friday."
Tan Lap gained attention in July when after police charged 50 people with smuggling heroin into prisons.
DPA