Fifteen inmates escaped from a prison near Uganda's capital Kampala after using water and urine to weaken the prison walls, Prisons Service spokeswoman Mary Kaddu said on Friday.

"This prison is very very old. The walls are very weak and the cells very small. These men must have used urine and water to weaken the spot where they escaped through. They must have co-ordinated their move ... they must have planned this for a very long time," Kaddu said.

The jailbreak occurred on early Thursday, and a police spokesman said the inmates celebrated their new-won freedom by engaging in a robbery spree.

According to police spokesman Asuman Mugenyi, the escapees used spoons, electric bulb holders and metal bars to dig their way through the weakened wall while prison guards apparently had fallen asleep.

The robberies were committed in a neighbouring village. None of the 15 has been apprehended, he said.

The convicts, on remand for charges including robbery, treason and murder, were inmates at the Kigo prison, about 15 kilometres south of Kampala.