Boston - An elite field of runners from 11 countries began racing on Monday morning in the 120th Boston Marathon, the world's oldest continually run annual marathon.
It was the third running since a pair of ethnic Chechen brothers killed three people and injured more than 260 with a bombing attack at the finish line.
Ethiopian Lelisa Desisa will bid for his third title against 20 other competitors from nine countries, including two previous winners from Kenya.
On the women's side, Kenyan Caroline Rotich took to the course to defend last year's crown, but will face pressure from Ethiopia's Tiki Gelana, who won gold at the 2012 Olympics.
Most top U.S. marathoners are sitting out Boston to train for the Rio Games in August, but Kenya and Ethiopia have yet to pick their teams and will consider the Boston results.
The men's elite field took off from the starting line in the Boston suburb of Hopkinton at 10 a.m. EST (1400 GMT), about a half hour after the women's elite.
Tens of thousands of amateur competitors stretched and soaked up the sun, waiting to try the notoriously challenging course.
“It's always been a dream of mine to run Boston,” said David Harris, 42, of Atlanta.
Open divisions start around noon. In total, about 30,000 people are expected to attempt the course.
Known as a tactical racer with a sprint finish, men's elite headliner Desisa posted a personal best of 2:04:45 in Dubai in 2013. He won Boston in 2:09:17 last year and also won in 2013.
Kenya's Geoffrey Mutai enters the race with the fastest personal time of 2:03:02, a course record he set with his 2011 Boston win. Kenyan Wesley Korir whose personal best is 2:06:13, is returning for the fourth time after having won in 2012.
Meb Keflezighi, who became the first American to win Boston in more than three decades when he scored an emotional victory in 2014 on the anniversary of the bombings, said he would sit out Boston to prepare for the Olympic marathon.
The year that Keflezighi won saw a near-record number of runners and throngs of cheering spectators packing the sidelines and was hailed as a symbol of the city's recovery from the bombing attacks.
The men and women's winners this year will receive $150 000. – Reuters