At least three men wearing dark clothes and balaclavas attacked a prison van in Manchester and threatened staff transporting the prisoners with a shotgun, police said.
The men arrived at the scene in a dark coloured Saab and freed prisoners Ryan MacDonald, 20, and Stevie McMullen, 31, Greater Manchester Police said.
The five men then got back into the car and drove a short distance before abandoning it.
Police believe they ran towards Phoebe Street in the Ordsall estate and that two possibly then rode a motorbike found abandoned on Thurlow Street.
More top news
Divisions among MPs and party supporters have intensified in recent weeks amid an increasingly fraught leadership battle.
Stephen Port, 41, is already accused of drugging and murdering four men he met on gay websites before dumping their bodies near a church.
Nicola Sturgeon said it is her job as Scottish First Minister "to explore every option to protect Scotland's interests" in Europe.