Two prison guards taken hostage at a penitentiary outside the Swedish city of Eskilstuna by two men convicted of serious crimes have been freed, according to local media.

       At lunchtime on Wednesday the convicts broke into a guard room in Hallby Prison armed with razor blades and barricaded themselves in with the hostages.

       Swedish tabloid Aftonbladet said the pair demanded a helicopter for their use and 20 kebab pizzas for themselves and other inmates on their ward.

       Pictures were later published showing pizzas being loaded into a car in Hallby, understood to be bound for the prison.

       The Swedish Prison and Probation Service said it was a "very dangerous situation" The Swedish news agency TT said the pair were convicted murderers aged 24 and 30.

       "The inmates have been convicted of serious crime," the probation service's acting security chief Jorgen From Nordin told TT. "The Swedish Prison and Probation Service's negotiators, task force and police are onsite and the situation is frozen."

       By 9.30pm local time both of the guards had been freed and were unharmed, according to Dagens Nyheter. The two prisoners have been taken to Eskilstuna police station.

       Eskilstuna is around 120 kilometres (75 miles) west of the capital, Stockholm.