Usain Bolt completed his third straight clean sweep of Olympic sprint events on Friday by leading Jamaica to victory in the men's 4x100m relay final here at the Rio Games.

Jamaica, also represented by Asafa Powell, Yohan Blake and Nickel Ashmeade, clocked 37.27 seconds to beat Japan by 0.33 seconds, with Canada taking bronze in 37.64. The United States and Trinidad and Tobago were disqualified for illegal exchanges.

Earlier on Friday, Liu Hong's long wait for an Olympic medal came to a happy ending when the Chinese world record holder won a thrilling 20km race walk.

The 29-year-old clocked one hour 28 minutes and 35 seconds to beat Mexico's Maria Guadalupe Gonzalez by just two seconds.

China's Lu Xiuzhi took bronze, only seven seconds behind her teammate.

"It was hard because the weather wasn't that good," Liu said of the hot conditions. "The only thing I could do was keep going, do my best and try to make it perfect."

Italy's Antonella Palmisano was fourth and China's Qieyang Shijie fifth.

Liu finished fourth in the race at both the Beijing 2008 and London 2012 Olympics. She rebounded from those setbacks by posting a world record of 1:24:38 in Spain last year.

"It means a lot to me. I have been doing this sport for more than 10 years now," Liu added. "This time I was doing my best to get a medal and I am pleased I could get the gold."

Bolt began the final leg of the relay race trailing Japan's Aska Cambridge but quickly caught his rival before surging clear in the last 50m with his trademark burst.

The victory gave Bolt his ninth Olympic gold medal and secured an unprecedented three consecutive titles in the 100m, 200m and 4x100m relay.

The 29-year-old won the 100m gold here by defeating long-time rival Justin Gatlin on Sunday. And on Thursday he clinched the 200m title by finishing ahead of Canada's Andre de Grasse.

Jamaica's 4x100m relay triumph concluded a day of athletics in which seven gold medals were decided in Rio's Olympic stadium.

On women's part, the United States clinched its 11th Olympic women's 4x100m relay title, setting the second fastest time in history.

Allyson Felix, Tianna Bartoletta, Tori Bowie and English Gardner clocked 41.04 seconds, beating a fast-finishing Jamaica by 0.35 seconds. Britain was third in 41.77.

It was Felix's fifth Olympic gold medal and the third for Bartoletta, who also won the long jump here.

The time was just 19 hundredths of a second slower than the world record set by the US at the London 2012 Games, in which Felix and Bartoletta participated.

The US originally missed out on qualifying for the final but was allowed a solo re-run of its heat on Thursday when officials ruled its runners were obstructed.

Kenya's Vivian Cheruiyot clocked 14 minutes and 26.17 seconds to set a new Olympic record, clinching gold in the women's 5000m.

The 32-year-old's time beat the previous mark held by Gabriela Szabo of Romania by more than 14 seconds.

Kenya's Hellen Onsando Obiri took silver in a personal best 14:29.77 with Ethiopa's Almaz Ayana grabbing bronze in 14:33.59.

Dilshod Nazarov, 34, won the men's hammer throw to secure Tajikistan's first gold medal after recording a best throw of 78.68m to beat two-time world champion Ivan Tsikhan of Belarus by 0.89m. Poland's Wojciech Nowicki claimed bronze with a best effort of 77.73m.

Greece's Ekaterini Stefanidi claimed gold in the women's pole vault, defeating Sandi Morris of the US, while Slovakia took their first ever Olympic track and field gold when Matej Toth charged home to win the 50km race walk.