Boston Marathon explosions: two dead and 23 injured – live updates

As we mentioned earlier, the Boston Marathon has referred to bombs. The reference comes in a post on its official Facebook page. "There were two bombs that exploded near the finish line in today's Boston Marathon," reads the message, posted about a half hour ago. "We are working with law enforcement to understand what exactly has happened." Boston explosion: the scene near Copley Square, captured by Twitter user @boston_to_a_t

 
People react to an explosion at the 2013 Boston Marathon on Monday.
 Photograph: John Tlumacki/AP
 
Police clear the area at the finish line of the 2013 Boston Marathon following 
at least one explosion. Photograph: Charles Krupa/AP
 
Police officers with their guns drawn hear the second explosion down the street. 

The first explosion knocked down a runner at the finish line of the 117th Boston Marathon. 

Vice president Biden, in a statement, has referred to a "bombing," not an "explosion," Dan Roberts reports in Washington. "Our prayers are with those people in Boston who have suffered injuries," Biden said. The marathon's organisers have also referred to "bombs". But there is no official confirmation of that from law enforcement agencies yet.

Police departments in New York City, Washington and elsewhere are on heightened alert.
"We're stepping up security at hotels and other prominent locations in the city through deployment of the NYPD's critical response vehicles (CRVs) until more about the explosion is learned," New York police spokesman Cheryl Crispin tells the Guardian's Karen McVeigh.

A large number of runners, spectators and others appears to still be in the finish area and surrounding blocks. Police are asking people to leave the area and stay away. Not all runners had finished the race when the explosions happened. The race brings a large number of people into the streets.

 
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. Photograph: AP/WBZ TV
 
Medical workers aid injured people at the finish line of the 2013 Boston Marathon 
following an explosion. Photograph: Charles Krupa/AP