Britain's Sports Minister Hugh Robertson says the London Marathon will go ahead as planned on Sunday and is "absolutely confident" that it can be kept safe.
Three people died and up to 150 others were injured yesterday after near simultaneous explosions at the finish line of the Boston marathon.
Asked if he believed the London Marathon should still take place, Robertson told the BBC Radio 4 Today programme: "Yes, I do.
"These are balance of judgments but we are absolutely confident here that we can keep the event safe and secure.
"I think this is one of those incidents where the best way to show solidarity with Boston is to continue and send a very clear message to those responsible."
— Paula Radcliffe (@paulajradcliffe) April 15, 2013
Situation looks awful, thoughts with everyone. There are some very sick people out there, who would do something like this?
Boston Police Commissioner Ed Davis told a news conference last night that there had been two "simultaneous explosions" near the finish line of yesterday's 26.2-mile event.
"Each scene resulted in multiple casualties," he said.
Speaking to BBC Radio Five, Nick Bitel, chief executive for the London Marathon, said: "We will not be cancelling. What we are doing, we are reviewing.
"You look at what has occurred, if there are steps we can take to increase security and all sorts of measures one could deploy.
"We run through the city. When you have an event of any nature - a marathon, parade... it's only as safe as the city itself. If it's not held in a stadium you can't do a lockdown like you may do in a building."
"When you have an event of any nature - a marathon, parade... it's only as safe as the city itself" - Nick Bitel
David Lowe, a specialist in security at sports events, said security at the funeral of Lady Thatcher and at the London Marathon would be as "tight" as possible.
"I think you are going to find a lot of surveillance on the crowds, it is the classic of not those watching the race - those who may be looking around, acting slightly different, slightly more suspicious," he told BBC Breakfast.
"There could be people looking elsewhere for totally different reasons - I can imagine that the security will be stepped up.
"Of course we have the funeral of Margaret Thatcher tomorrow, you will have people protesting who feel vehemently about her premiership.
"Again, there will be high security for that because there will be people lining the streets to pay tribute to Margaret Thatcher.
"We have the two events where we have got to make sure, certainly the security services and the police, have got to make sure it is as tight as possible."
In an earlier statement, Bitel said: "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."