Athletics:Olympic sprint champion Usain Bolt won his third gold of the Games when he anchored Jamaica to victory in a blistering men's 4 x 100 metres final as they retained their title in a world record 36.84 seconds on Saturday night.
It was the same Jamaican quartet of Nesta Carter, Michael Frater, Yohan Blake and Bolt that had set the previous mark of 37.04 at the world championships in Daegu last year.
The United States team of Trell Kimmons, individual bronze medallist Justin Gatlin, Tyson Gay and Ryan Bailey won silver in 37.04 to equal the old record.
Canada finished third but were disqualified for a lane infringement, leaving the athletes in tears on the track as Trinidad and Tobago were awarded the bronze in 38.12. The Canadians have appealed against the decision.
US lead-off man Kimmons got a flying start and the Americans appeared to have the initial edge but by the third leg Jamaica's 100 and 200 silver medallist Blake came off the bend level with rival Tyson Gay and once Bolt got the baton there was only ever going to be one winner.
To a tumultuous noise, Bolt pulled away from Bailey and, for once, kept going all the way to the finish even dipping for the line.
Bolt, who now has six Olympic gold medals from two Games, wanted to keep the baton but track officials would not let him, resulting in boos from the 80-000 strong crowd.
The Jamaicans then went on a lap of honour, high-fiving and kissing members to the crowd.
Allyson Felix claimed her third gold medal as the United States outclassed their rivals to win the women's 4 x 400m relay by some distance.
Felix, who took the 200 metres individual title and was part of the 4 x 100m team that smashed the 27-year-old world record on Friday, ran the second leg to help the Americans cross the line first.
There was to be no world record in the one-lap relay, though, with Sanya Richards-Ross powering across the line in three minutes, 16.87 seconds, outside the mark of 3:15.17 set by the Soviet Union at the 1988 Seoul Olympics.