The London Marathon will definitely go ahead on Sunday but security is being scrutinised, organisers said, after explosions near the finish line of the Boston race killed at least three people and wounded more than 130.
The Boston blasts appeared to go off near where spectators stood behind roadside barriers. One runner was seen collapsing to the ground as he heard the blasts.
It was the worst bombing on US soil since security was tightened after the attacks of September 11 2001, and President Barack Obama promised to hunt down whoever was responsible for the attack on a day when tens of thousands of spectators packed the streets to watch the world-famous race.
Britain's double Olympic champion Mo Farah is one of 36,000 runners set to compete in the 41.84 kilometre London race, which starts at Greenwich Park and winds through some of the city's iconic landmarks before finishing at the Mall.
"We will be reviewing our security arrangements in partnership with the London Marathon," Metropolitan Police chief Superintendent Julia Pendry said in a statement.
The London race was first run in 1981 and has become a centrepiece of the sporting calendar in Britain with elite athletes being joined by the vast number of amateur runners who compete to raise money for charity.
"We are deeply saddened and shocked by the news from Boston," London Marathon Chief Executive Nick Bitel said in a statement.
"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," he said.
The US Federal Bureau of Investigation has taken the lead on the investigation with help from several other US federal, state and local law enforcement agencies.
The two explosions at 2:50 pm Boston time were about 50 to 100 metres apart as runners crossed the finish line with a timer showing 4 hours and 9 minutes, some nine minutes faster than the average finish time, as reported by Runner's World magazine.
Reuters