Three dead and over 140 injured in explosions at Boston Marathon finish line

Update 16 April: Three people have been killed, including an eight-year-old boy and more than 140 others hurt after two bombs exploded during the Boston Marathon. Officials say that at least 17 people are critically wounded and the injuries include several amputations.

The attached video captures an explosion. The uploader said: "This is a video my mom recorded of the explosion. We are so lucky we got out of there when we did. My mom didn't finish the race but we are all safe and that's what matters. My heart goes out to victims". (NekoAngel3Wolf/NewsPoint)

The FBI has taken over co-ordination of what it described as a "potential terrorist inquiry" and Boston police say officers are working around the clock and all leave has been cancelled. The scene of the explosions has been cordoned off and is expected to remain so for the rest of the day.

15 April: Two people are confirmed dead and at least 50 have been reported injured after two explosions near the finish line of the Boston Marathon.

Boston Police report the explosions happened "simultaneously" on Boylston Street at around 2.50pm American east coast time (7.50pm UK time). This would have been approximately 2 hours after the race winners would have crossed the finish line. A third incident initially thought to be a third explosion at the JFK Library in the city, appears to have been unrelated - possibly the result of an electrical fire.

In a statement, police said that they are treating the incidents as "an ongoing event at this time".

President Obama assured Boston leaders of the full support of the federal government and sent his thoughts and prayers to the victims. He said: "We will find out who did this and we will hold them accountable".

Initial reports from Boston suggested the first and second blasts may have come from in or around the Fairmont Copley Plaza Hotel.

Police have confirmed that a police controlled explosion also took place.

Police are looking for any information the public can provide. They are treating all baggage in the area - some of which was discarded by public fleeing the scene - as potentially suspicious.

Public in the city have been advised to stay indoors and not to congregate in large groups. A no fly zone has been implemented over the city and the cellphone service to the area as been shut down to prevent mobile detonation of explosions.

Runners who were still taking part in the race were quickly re-routed.

Many of the injured were attended to by medical workers who had been stationed near the finish as part of the race support team.

Emergency services continue to work at the scene.

Police in New York have stepped up security in the city around popular sites and hotels in reaction to the events in Boston.

Police in Boston expect to provide a further briefing at approximately 7pm Boston time (midnight UK time).

The troubling scenes come less than a week ahead of the London Marathon next Sunday. The Chief Executive of the London Marathon, Nick Bitel, has given his reaction to the news from Boston:

"We are deeply saddened and shocked by the news from Boston. Our immediate thoughts are with the people there and their families. It is a very sad day for athletics and for our friends and colleagues in marathon running.

"Our security plan is developed jointly with the Metropolitan Police and we were in contact with them as soon as we heard the news."

Met Police Chief Superintendent Julia Pendry said:

"A security plan is in place for the London Marathon. We will be reviewing our security arrangements in partnership with London Marathon."

Prime Minister David Cameron wrote on Twitter: "The scenes from Boston are shocking and horrific - my thoughts are with all those who have been affected."