Three people were killed at the finish line of the Boston Marathon at Copley Square at 2.50 pm local EST yesterday. Over 140 people were injured.
The US Congress commemorated the victims with a minute's silence. UN Secretary General Ban Ki-moon condemned the organizers of the blast.
The bomb was probably activated using a cellphone. Communications in Boston were shut down 40 minutes after the blast.
Five more bombs were found and neutralised in the area.
Security has been enforced at the White House and Pentagon. New York City is being patrolled by thousands of officers.
24 Russians took part in the marathon. Nikolai Perunov was not injured and crossed the finish line before the blast. The Consulate General says that only 19 Russians were running, three of them were far away from the explosion.
