World leaders and international sports bodies have sent messages of support to the victims of Sunday's Boston Marathon twin explosions. Focus is also turning to the security of major events coming up this week.
The German foreign minister, Guido Westerwelle, said he was "deeply shocked" by the events in Boston "and their terrible consequences."
"What should have been nothing other than a traditional, entertaining sports event for tens of thousands of runners and hundreds of thousands of spectators in Boston and around the world, has become a tragedy," he said on Tuesday in Berlin.
"We express our sympathies to the family and friends of the victims," Westerwelle said.
US President Barack Obama warned against "jumping to conclusions" as to identifying perpetrators, however the news agency AFP has quoted a senior White House official, speaking on condition of anonymity, that such an attack was "clearly an act of terror."
The outgoing Italian prime minister Mario Monti condemed the attack as a "cowardly act of violence that prompts distain and leaves us shocked," and sent a message of support to Obama on Tuesday.
Russian President Vladimir Putin also offered his country's assistance in investigating the bombings, in a message of condolence on the Kremlin's website.
The International Olympic Committee also sent its support in a statement from President Jacques Rogge.
"My thoughts and those of all the Olympic Movement are with the victims, their friends and their families today," Rogge said.
Security beefed up
The explosions forced cities across the United States to go on high alert, evoking memories of the September 11, 2001 attacks.
A number of other marathons are due to be held around the world in the coming weeks, throwing their security into the spotlight.
"We fully expect that Sunday's race, registration and associated events will go ahead as originally scheduled," the organizers said in an email to participants. They added they were "deeply saddened and shocked by the news from Boston."
"We are currently reviewing all our security arrangements with the Metropolitan Police," the email said.
Speaking to BBC radio, Sports Minister Hugh Robertson told BBC radio he was "confident" the event could be kept 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," said Robertson.
Police in London are already preparing for a large security operation, for the funeral of former British prime minister Margaret Thatcher, to be held on Wednesday. Thatcher's coffin is to travel through the streets of London on a horse-drawn carriage ahead of the service at St. Paul's Cathedral.
The ceremony will be attended by Queen Elizabeth II and other world leaders and dignitaries.
Meanwhile, organizers of Japan's Nagano Marathon said its race will go ahead as planned this week.
"We will have closer communications with police and security officers to make sure the race takes place without any problems," said Makoto Yajima, a spokesman for the marathon organisers.
The former Australian champion runner, Robert de Castella, who won the Boston title in 1986, urged organizers to not bow to terror threats. He was close to the finish line on Monday when the explosions occurred.
"I am of the view that the last thing we should do is kowtow to this sort of coward action, and [should] continue to do what we always have done," de Castella told the national public broadcaster, the ABC.
"If it is an act of terrorism, then obviously these things are designed to disrupt people's participation in events like this and I think that is exactly what they are trying to achieve," he said.
jr/kms (AFP, AP, Reuters)