China, the US and Ethiopia each won gold medals on the opening day of athletics at the Rio Olympics on Saturday.

Wang Zhen was the first track and field champion of the Games, powering to victory in the men's 20km race walk.

The 24-year-old finished in one hour 19 minutes and 14 seconds, falling just 28 seconds short of the Olympic record set by his countryman Chen Ding at the London 2012 Games.

China's Cai Zelin took silver, 12 seconds behind Wang, with Australia's Dane Bird-Smith third in 1:19.37.

"I feel like I didn't have much of a plan about this race," Wang said. "I talked with my coach beforehand, but I just followed my heart. I picked up my pace with about three kilometers remaining, despite the fact my coach wanted me to wait until later."

Bird-Smith did not hide his delight at securing the bronze medal, and paid tribute to Cai and Wang.

"I knew they were going to come out hard," he said. "I didn't know when it was going to happen, but as they went for it I thought, 'I got to get on their tails, and I got to go for it'.

"They took off with about 4km to go. They were the ones I was watching throughout the race. I wasn't going to let them slip away. Not without a fight. As soon as they went, they went hard. And they kicked hard.

"I probably wasn't expecting when they went. As soon as they hit it they went off like absolute rockets. I reeled them in and you know I was only a couple of seconds behind the whole way and I maintained that gap. I can't be happier with it."

Ethiopia's Almaz Ayana said she was "in awe" after smashing the world record to win the 10,000m.

The 24-year-old finished in 29 minutes 17.45 seconds, to break the previous record held by China's Wang Junxia by more than 14 seconds.

Kenya's Vivian Cheruiyot, who took bronze at the London 2012 Games, was second in 29:32.53. Defending champion Tirunesh Dibaba of Ethiopia grabbed bronze in 29:42.56.

"This means everything to me," Ayana said. "It's a huge deal. I never thought that this would happen. I'm so in awe.

"I have worked very hard. I wouldn't say that my recent training has been any different from before but it was hard and it was all worth it."

Ayana, the 5,000m world champion, was racing over 10,000m for only the second time in an official competition.

In June she registered the fastest 10,000m debut in history with 30:07.00 at the Ethiopian Olympic trials.

She is the first woman to set a 10,000m world record at an Olympic Games.

In the day's final gold medal decider, the USA's Michelle Carter won the women's shot put by coming from behind to defeat defending champion Valerie Adams.

Carter looked set for the bronze medal before throwing a personal best 20.63m with her last attempt.

Adams was the firm gold medal favorite, having won the event at the Beijing 2008 and London 2012 Games. But the New Zealander was relegated to the silver medal with a best throw of 20.42m.

Hungary's Anita Marton clinched bronze with a best attempt of 19.87m.

Source : XINHUA