The FBI has released images and video footage of two men suspected of being involved in the Boston Marathon bombs.

The footage shows the men carrying backpacks on a crowded footpath near the finish line.

Three people were killed and over 170 injured in the blasts on Monday.

Speaking at a news conference, FBI Special Agent in Charge in Boston, Richard DesLauriers warned that the men are considered "armed and dangerous".

He identified suspect No. 1 as a man wearing a dark baseball cap and sunglasses, whilst Suspect No. 2 wore a white cap baseball cap backwards and was seen setting down his backpack on the ground.

The video was taken about 13 minutes before the two explosions.