Two Greek police officers have been shot dead with their own weapons as two prisoners escaped during a jail transfer, authorities say.
The inmates, an Albanian and a Russian, escaped from a prison van near the northern town of Trikala.
The prisoners had requested a toilet stop, but then seized the officers' weapons and opened fire on them.
A third prisoner, another Albanian, stayed at the scene and was later taken back into custody.
A massive search for the prisoners, involving helicopters and special police forces, was launched following the attack.
The Russian escapee is reported to be serving life for murder.
All three prisoners were being transferred from prisons in Corfu and Ioannina to another in the city of Larissa, the AP news agency said.
The incident occured just after 1100 local time (0900 GMT).