Prison guards have discovered a 'narco cat' roaming around a Costa Rican jail with marijuana and crack strapped to its body.

According to a statement on Facebook from the country's Ministry of Justice, officers at the Pococi Penitentiary spotted the unlikely smuggler on the prison grounds on May 6 before capturing it.

Prison staff were suspicious of grey patches on the feline's fur and decided to take a closer look.

The patches turned out to be bags filled with narcotics - including a bag containing 236 grams of marijuana, and another containing 86 grams of crack cocaine.

Footage shows the moment prison officers found the feline felon as it climbed a tree on prison grounds.