"A security plan is in place for the London Marathon," The Daily Telegraph quoted Metropolitan Police Chief Superintendent Julia Pendry as saying. "We will be reviewing our security arrangements in partnership with London Marathon."
London Marathon Chief Executive Nick 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."
Race organizers expect an estimated 36,000 runners to take part Sunday.