LONDON (AP) — For Geoffrey Mutai, the bombs that ripped through Boston stripped away some of the innocence and freedom from marathon running.

Mutai watched from afar on Monday as the scene of one of his great triumphs two years ago turned into one of horror.

With three people killed and more than 170 wounded by the twin blasts near the Boston Marathon finish line, Mutai is apprehensive as he prepares to take on the London Marathon on Sunday.

The Kenyan says the unknown perpetrator — or perpetrators — have "taken our freedom which we normally have in races ... it will be challenging for the sport."

But he says "if you are thinking something like that (bombings) can happen you can't concentrate."

Runners will wear black ribbons on Sunday.