Terrified commuters were hauled off an Edmonton bus after a terror alert.

Nervous passengers raised the alarm after spotting an unattended large, black bag on the lower deck of a 259 bus at around 2.20pm on Thursday.

Police officers arrived within minutes to evacuate around 20 passengers from the bus, which was travelling along Fore Street near the junction of Glover Street.

Sniffer dogs able to hunt out explosives were taken to the scene as amazed residents looked on, fearing another attack on the capital's transport system.

But their fears proved groundless after the cordons were taken down shortly before 4pm and explosives experts confirmed no device had been found at the scene.

Det Supt David Eyles said: "I am disappointed that people are being careless with their personal belongings when there are four suspected suicide bombers at large because a number of police resources were assigned to that call and all these officers could have been better deployed."

He added: "My feeling is the public are right behind us, even though the increasing number of security alerts on trains, Tubes and buses can make their day longer.

"It is good that the public have been highlighting their concerns. We need people to be vigilant."