Boston Police Manhunt For Marathon Bombings Suspect: In Pictures

Pictures of the Boston Marathon bombing suspects have emerged for the first time, alongside dramatic images of a shoot-out and explosions in Watertown and at MIT, where a police officer was killed.

One suspect is dead and another still at large.

A police spokesman described the man they were looking as a "terrorist", of Caucasian descent with curly brown hair, adding that he was armed and dangerous. Police have warned residents to stay in their homes.

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Officials said the streets were now in lockdown as they searched for the man who was first pictured in CCTV from the Boston Marathon wearing a white hat. They refused to name either suspect.