A pair of explosions have killed at least 3 people and injured over 140 others at the Boston Marathon in the US. Two bombs exploded almost simultaneously in the packed streets near the race finish line.

An 8-year-old boy was among the dead. And hospitals say at least 17 of the injured victims are in critical condition. Most of the wounded were spectators. The blasts occurred near the finish line, and two more bombs were reportedly found nearby and safely dismantled.

Massachusetts State Police confirmed that a search warrant was executed Monday night on a flat in the Boston suburb of Revere, but provided no further details. Mobile connections in Boston were temporarily cut off to avoid more possible blasts being triggered by cellphones. The Federal Aviation Administration also created a no-fly zone over the city. And two nuclear power stations near Boston were put under tighter security.

A fire was also reported at the John F. Kennedy presidential library, but police say it was unrelated to the bomb attacks and there were no casualties. The US Capitol lowered its national flag to half-mast to mourn the victims. So far, no one has claimed responsibility for the attack, and police said they have no suspects in custody.