Tsegaye Kebede and Priscah Jeptoo win emotional London Marathon that included tribute to Boston victims

Ethiopia's Tsegaye Kebede and Priscah Jeptoo of Kenya triumphed at a sombre London Marathon on Sunday, as runners paid tribute to the victims of the deadly bomb attacks at the Boston Marathon.

Kebede hunted down 2011 champion Emmanuel Mutai to win the men's race, while Jeptoo surged to victory in the women's event, eight months on from her second-place finish at the London Olympics.

The men's and mass races were preceded by a 30-second silence in memory of the three people killed and around 180 injured in Monday's bombings in Boston, while competitors donned black ribbons in tribute.

After a frenetic start in the men's race, Mutai led Stanley Biwott, Feyisha Lilesa and Ayele Abshero past the 30-kilometre mark just 10 seconds outside world-record pace.

Biwott tried to force the issue but Mutai resisted his Kenyan countryman's efforts to break clear and found himself in the lead.

However, he began to flag badly as he approached the Houses of Parliament and Kebede tore past him to cross the line in a time of 2hr 06min 04sec. Mutai trailed in second, with Abshero third.

British Olympic star Mo Farah had helped set the early pace before dropping out, as planned, after an hour.

The 5,000 and 10,000 metres champion at last year's London Games is preparing to compete over the full distance next year and he said he had struggled with some of the specific demands of marathon running.

"The pace is not a problem. The biggest challenge is picking up the right drink and I think I made a mess of it," Farah said.

"I've learnt the biggest lesson of my life, really. If I come here next year and make a mess of it, it'd be hard to deal with, so it's opened my eyes."

Jeptoo, who finished third in last year's race, streaked away from the women's field to claim victory ahead of compatriot Edna Kiplagat and Yukiko Akaba of Japan.

London Olympic champion Tiki Gelana collided with men's wheelchair athlete Josh Cassidy at a drinks station after 52 minutes and the Ethiopian's challenge never recovered.

As Gelana toiled, Jeptoo led a three-woman breakaway that also featured world champion Edna Kiplagat and 2011 Berlin Marathon champion Florence Kiplagat.

Florence Kiplagat slowly fell back and her namesake Edna could not keep pace with Jeptoo either after the 28-year-old ran the 21st mile in a time of five minutes and 11 seconds.

Jeptoo completed the race's final stages alone and raised her arms in triumph as she crossed the finish line in front of Buckingham Palace in a time of 2hr 20min 15sec.

"Today I'm very, very happy. I couldn't believe I could be the winner," Jeptoo said.

"It is a very tough race because everybody who comes here is really prepared."

Australia's Kurt Fearnley took the honours in the men's wheelchair race after pipping Marcel Hug of Switzerland in a sprint for the line.

Britain's David Weir, who was bidding for a seventh London Marathon title, was level with Hug as the leading racers entered the final straight but ultimately finished fifth.

American Tatyana McFadden claimed victory in the women's wheelchair event in a course record time to follow up her success in the equivalent race in Boston.

Earlier, 35,000 runners bowed their heads and observed a moment of reflection in memory of the victims of Monday's devastating twin bomb blasts in Boston.

Organisers have pledged to donate £2 ($3, 2.30 euros) for every finisher to a fund for the Boston victims.

Meanwhile, the police presence along the 26.2-mile (42.2-kilometre) course was increased by 40 percent.

Despite security fears, organisers said 700,000 people had taken to the streets of London to watch the race on a day of blue skies and bright sunshine in the British capital.

US police arrested one suspect in the Boston bombing on Friday after his brother and fellow suspect was killed in a shootout.