London Marathon security tightened after Boston bombings

While the city is unfortunately familiar with bomb threats, organizers of Sunday's London Marathon are still taking extra precautions following the bombings in Boston.

An estimated 700 extra police officers are to bolster already tight security when runners begin the race.

"There are no gaps because obviously we police this every year,” Metropolitan Police representative Julia Pendry told ITV News.

"What we have done since Boston is we've reviewed our plans, we've reviewed our contingencies and I have put on increased numbers of officers in high visibility reassurance patrols."

The London marathon is one of the world's largest, with 36,000 athletes participating and another 650,000 spectators.

It's the first marathon since Monday's violence in the United States.

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The race will begin with a moment of silence in memory of the three people killed and 176 injured in Boston on Monday.

Brothers Dzhokhar and Tamerlan Tsarnaev are the only suspects in Monday's attack that saw two bombs explode near the finish line.

They held the city hostage all week trying to elude police before they were caught. Tamerlan died during the pursuit while Dzhokhar was seriously wounded.

London race organizers will also donate $3 for every runner to Boston charities, BBC said.

With the suspects caught or dead, everyone in London and Boston are breathing easier now.

"In terms of our preparations, it's all gone well," London marathon executive Nick Bitel told BBC.

"Obviously there were some additional security issues following Boston, but that seems to be bedding down and the message of reassurance to runners has been very well received."

If the Tsarnaev brothers were somehow connected to a network of terrorists targeting marathons, London is certainly another prize target.

Stars such as Olympic champion Mo Farah will lead the field past landmarks such as Big Ben, Parliament and Buckingham Palace, the New York Times said.

Yet, there is no evidence London is facing threats.

"There is no link between the Boston Marathon and the London Marathon, and there is no change to the threat level at this time to London," Pendry told The Times.

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