Boston bombings: The world reacts

Runners in the men's elite race of the 2013 Virgin London Marathon observe 30 seconds of silence in honor of the victims of the Boston Marathon bombings before the start of the race in London on Sunday, April 21. People worldwide expressed their condolences after at least three people were killed and scores wounded in two explosions Monday near the finish line of the Boston Marathon. <a href='http://www.cnn.com/SPECIALS/us/boston-bombings-galleries/index.html'>See all photography related to the Boston bombings.</a>

Runners in the men's elite race of the 2013 Virgin London Marathon observe 30 seconds of silence in honor of the victims of the Boston Marathon bombings before the start of the race in London on Sunday, April 21. People worldwide expressed their condolences after at least three people were killed and scores wounded in two explosions Monday near the finish line of the Boston Marathon. See all photography related to the Boston bombings.