Boston Marathon blasts: three killed, several injured

The explosives that killed three and wounded more than 170 at the Boston Marathon were in 6-litre pressure cookers and placed in black duffel bags that were placed on the ground. The duffel bags contained shards of metal, nails and ball bearings.

The chief FBI agent in Boston said that "we will go to the ends of the Earth" to find whoever carried out the deadly attack. An FBI agent in charge in Boston said that investigators had received "voluminous tips" and were interviewing witnesses and were analyzing the crime scene.

Two explosions at the finish line of the Boston Marathon have resulted in injuries. This picture taken seconds after the blast shows how people reacted to the explosion.

Bloody spectators were being carried to the medical tent that had been set up to care for fatigued runners.

Medical responders attend to an injured man.

Many of the injured are said to have had lost or injured their legs in the blast, witnesses said.

In this image from video provided by WBZ TV, spectators and runners run from what was described as twin explosions that shook the finish line of the Boston Marathon.

There was pandemonium as panicked runners and spectators scattered, and rescue workers rushed in to care for the injured.

Medical workers wheel the injured across the finish line.

A Boston police officer clears Boylston Street following the explosions.

A flag flies over the finish line as medical workers aid injured people following the explosions.

Medical workers and authorities work near the scene of explosion.

Helicopters fly near the construction site of One World Trade Center in Manhattan. New York is securing its city in the wake of explosions near the finish line at the Boston Marathon.

A runner in a wheelchair is taken from a triage tent after explosions went off.

A runner is escorted from the scene after explosions.

Reports in the US suggest investigation authorities have searched a flat in the Boston suburb.

Major roads leading to the blast sites have been cordoned off by the police.

Unclaimed finish line bags are viewed near the scene of a twin bombing at the Boston Marathon.

Staff stand outside a medical tent near the finish line of the Boston Marathon.