The London Marathon started as planned on a glorious sunny morning Sunday despite concerns raised by the bomb attacks on the Boston Marathon six days ago.

Some 36,000 runners took part as tens of thousands of others watched from the sidelines.Some runners wore black arm bands and ribbons pay tribute to victims of the Boston Marathon bombing last Monday.

Extra layers of security added by police and race organizers as a precautionary measure were also a feature.

Police said they planned to add 40 per cent more officers and extra surveillance, and police helicopters were in the air as the race got under way.

London's was the first major international marathon since the double bomb attack near the finish line in Boston. One suspect was killed during police attempts to capture him, while a second was later arrested.

London police and organizers said the extra measures would assure safety at the starting and finishing points of the popular event, which usually draws tens of thousands of fans to the city streets.

Victims of Boston bombing honoured

A 30-second moment of silence was held before the start of the event to honor those injured in the Boston Marathon. In addition, the marathon organizers plan to donate money to a Boston fund set up to help victims there.

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Prince Harry, right congratulates runner Emmanuel Mutai of Kenya, who placed second in the men's category of this year's Virgin London Marathon in central London. (Joel Ryan/Invision/AP)

The Monday bombing there left three people dead and more than 170 injured, including many who are still hospitalized. In addition, a policeman was killed during the search for the two suspected bombers.

Runner Martin Connell, 42, wore a picture of 8-year-old Boston bombing victim Martin Richard on his jersey in tribute to his young namesake.

"It's a sign of peace and goodwill," said the runner, an IT worker from near Liverpool.

The organizers of the London Marathon said they did not consider cancelling the event, which is a highlight of the sporting calendar.

Priscah Jeptoo of Kenya won the women's race in a time of 2:20:1.

The men's race was won by Ethiopia's Tsegaye Kebede in a time of 2:06:03.