Michael Dwyer / AP Boston Marathon 2013 men's winner Lelisa Desisa, left, of Ethiopia, greets Boston Marathon bombing victims Adam Davis, top right, and his wife Adrianne Haslet-Davis, Sunday, June 23, 2013, in Boston.

The men's champion of the 2013 Boston Marathon returned his winner's medal to Mayor Thomas Menino on Sunday to honor the city and those killed and injured in the bombings near the finish line of one of the world's top running events.

"Sport holds the power to unify and connect people all over the world," Lelisa Desisa of Ethiopia told the crowd through a translator. "Sport should never be used as a battleground."

More than 6,400 athletes gathered on Boston Common for the 10K organized by the Boston Athletic Association, the same nonprofit that handles the annual marathon. Spots for Sunday's race sold out in 13 hours online.

Brian Snyder, Reuters Lelisa Desisa of Ethiopia, left, champion of the men's 2013 Boston Marathon, presents his winner's medal to Boston Mayor Tom Menino during a ceremony in Boston, Massachusetts on June 23, 2013.

"Let me tell you: As mayor of this great city for the last several years, I have never seen Boston come together like it has after the attacks," Menino told the crowd. "Thank you for making Boston stronger."

A moment of silence paid tribute to the three victims killed in the April 15 bombings and to Sean Collier, the Massachusetts Institute of Technology police officer who was shot and killed April 18 in a search for the suspects.

"The feeling here is a little weird," said Jon Everitt, an MIT student who lives in Cambridge. He said the bombings are "definitely in the back of your head."

Melissa Blasczyk, of Boston, ran the 2013 Boston Marathon and was 1.5 miles from the finish line when spectators began telling runners the race was over.

"Today I'm going to finish, run a strong race and take in the scenery," she said. "Obviously, (the attack) is in the back of your mind, but you just have to live your life.