LISBON (AFP) - Gloria is a regular at Portugal's most infamous prison, but it isn't crime that keeps her coming back. The golden Barbado da Terceira is just one of the canine guests at a most unusual dog kennel run by inmates.

Owner Rui Silva checked in his pet, a shaggy Portuguese breed, for a weekend stay in the maximum security jail in Lisbon.

"It did not really faze me," the 48-year-old TV broadcast technician said about leaving his pet at the Monsanto prison, where Portugal's most notorious criminals are housed.

"I asked if they took good care of the animals, they said yes. That's what matters."

The inmates welcome the pets at the so-called Dog House in a modest reception area adorned by photos of former four-legged guests.

They verify vaccination records and receive instructions from pet owners. During the stay, they oversee feeding and bathing, walk the dogs and administer medication.

"It's a lot of responsibility," said Ricardo, an inmate serving a sentence for drug trafficking, as a pit bull licked his hand through the fence of its pen.

"What I really like is having contact with the public," the 34-year-old former bar owner said.

Giving inmates the chance to reboot relational skills and gain job experience is the goal of this unique project in Portugal.

The kennel, a white and yellow building, is located just outside the barbed-wire fence that surrounds the prison, a former military fort perched atop the highest point of Lisbon among pine and oak trees, with a panoramic view of the capital.

Its 68 dog pens usually fill up during peak vacation periods in summer and at Christmas, as well as over long weekends.

Two to five prisoners work at the kennel, depending on how busy it is. They receive a monthly stipend of around 80 euros (S$123) for their work.

"It is totally different than being inside, time goes by faster," said Ricardo, who was dressed in a red tracksuit and grey sweatshirt, as he pointed in the direction of the jail.

Married and with a young daughter on the outside, he said he was thinking of setting up his own kennel after he is released from jail at the end of the year.

The prison initially began the kennel for its staff but in 2000 it opened the facility to the general public.

The kennel charges 10 euros per day per dog, or just 9.50 euros if the owner brings the pet's own food.

Prison officials stress the kennel is not a business, but rather a tool to help rehabilitate prisoners and prepare them to return to society by giving them job skills.

"Looking after animals develops emotional ties which the inmates then project onto other people and society in general," Monsanto prison director Ana Cristina Carrolo Pereira Teixeira said.

And many of its regular customers like Silva, who first left his Gloria at the kennel several years ago, support those goals.

"Its being part of a prison maybe makes me want to use it even more, to help out," he said.

But not all prisoners at Monsanto, used to house the nation's most dangerous convicts, make the cut for kennel care.

Among the roughly 160 inmates currently held is an explosives expert with the Basque separatist group ETA who was arrested in Portugal in 2010, and the killer of two young policemen in a Lisbon suburb in 2005.

Those who can work at the kennel are selected from the approximately 20 prisoners who have been assigned to a less restrictive regime due to good behaviour.

"We try to pick ideal people for this role and that like being here," the kennel's veterinarian, Pedro Miguel Canavilhas de Melo, said.

Teixeira, the prison director, said she believes the inmates "are better people when they leave here in the way they relate to others because of their relationship with the animals."

"I think it calms inmates, their relationship with animals reduces aggression," she added.