US authorities have identified a possible suspect in the Boston Marathon bombings, but no arrests have been made.

Media quoted an anonymous US law enforcement source as saying that a male suspect had been identified thanks to security video footage. Two separate videos show a man leaving a bag at the scene before the blasts, which killed 3 people and injured over 170.

The FBI has postponed a press briefing on the progress of the investigation. An FBI spokeswoman said a bomb scare at the city's federal court house was the reason for the postponement.