Clement wins 400m hurdles but Culson in tears

Kerron Clement of the United States dipped on the line to win the men's Olympic 400 metres hurdles on Thursday after one of the pre-race favourites, Puerto Rico's Javier Culson, was disqualified for a false start.

Clement led down the home straight and was still clear going into the closing metres as he finished with a long, easy stride. But he had to lean into the tape to deny Kenya's Boniface Tumuti, charging up fast two lanes to his right.

Turkey's Yasmani Copello took the bronze, in a race thrown wide open by the failure of world champion Nicholas Bett of Kenya to make it through the heats.

Clement clocked 47.73 seconds to win by 0.05 of a second, with all the first five beating the previous best this season.

Culson, 32, bronze medallist in London in 2012, blew his chance by jumping the gun, and briefly sat sobbing by the side of the track before trudging away.

It was Clement's first major championship medal since he won the 2009 world title, having taken the silver at the Beijing Olympics the year before.

"It means so much. I was focused and my mind was set. I showed determination and a will to win and this is something I wanted with all my heart," the 30-year-old said.

Thomas Barr of Ireland came fourth, narrowly failing to win Ireland's first Olympic medal on the track since Sonia O'Sullivan took silver in the 5,000m at the Sydney Olympics in 2000.

"If you can't be happy with a lifetime best ... I would be lying if I said I was complaining, but I was so close - 0.5 of a second, and I think I could have found it," the Irishman said. "Fourth is the worst place, as you are so close."