Armenian President Serzh Sargsyan issued a letter of condolence to his U.S. counterpart Barack Obama over Boston blasts.

President Sargsyan condemned the crime and offered deep condolences to Obama, families of those killed and the U.S. people in general, wishing speedy recovery to those injured, presidential press services reported.

At least three people have been killed and more than 100 injured, some seriously, in two explosions at the finish line of the Boston Marathon Monday, April 15.

The first explosion came at about 14:50 local time (18:50 GMT), approximately two hours after the winners crossed the line. There was a loud explosion on the north side of Boylston Street just before the finish line sending some runners tumbling to the pavement while others were knocked down by those rushing to the scene.

Another loud explosion occurred a few seconds later, and smoke rose from the scene of the blasts. A fire then broke out at the John F Kennedy presidential library a few miles away from the finish line.

Police said it might have been caused by an incendiary device but it is unclear whether it is related to the bombings.