Organisers of the London Marathon have confirmed Sunday's event will still go ahead after three people died following a terror attack on the Boston Marathon yesterday.

In an email to entrants, Hugh Brasher, race director of the Virgin London Marathon said: 'We are deeply saddened and shocked by the news from Boston.

'Our immediate thoughts are with all the people there and their families. It is a very sad day for athletics and for our friends and colleagues in marathon running.

'We fully expect that Sunday's race, registration and associated events will go ahead as originally scheduled.'

The FBI is today hunting those responsible for a terror attack on the Boston Marathon which left at least three people dead, including an eight-year-old boy.

Scores were injured, many suffering shrapnel wounds, in the two blasts which rocked the finish line.

Massachusetts General Hospital said 'several amputations' had to be performed on survivors.

Police were searching a flat in the Boston suburb of Revere as part of the investigation. Massachusetts State Police confirmed that a search warrant was served last night but gave no more details.

There were no immediate claims of responsibility for the terror attack, the most serious in the US since the 9/11 World Trade Centre atrocity. Al Qaida-linked groups and militant white extremists have attacked targets in America in the past.

President Barack Obama, speaking from the White House, avoided using the words 'terror' or 'terrorism', saying officials 'still do not know who did this or why'.

In a televised address, he said those responsible will feel the 'full weight of justice'.

However, a White House official later said the explosions at one of the world's oldest and most prestigious marathons was being treated as terrorism.

•Do you still plan to take part in the London Marathon this weekend? Contact Lucy Wright on 01603 772439 or email lucy.wright@archant.co.uk