Sun Yang responded to taunts about his doping history in emphatic fashion on Monday by becoming the first Chinese swimmer to win the Olympic men’s 200 metres freestyle gold medal.

Sun, silver medallist in the event in London four years ago, touched the wall in one minute, 44.65 seconds to beat South Africa's Chad Le Clos by 0.55 seconds.

It was Sun's second medal of the Games after his silver in Saturday's 400 free. Conor Dwyer of the United States won bronze.

Monday’s victory was the third gold of Sun’s Olympic career, and sixth medal, adding to the 400 and 1,500 metres titles he won in London.

Britain's world champion James Guy, whose room-mate Adam Peaty stormed to breaststroke gold on Sunday and ended his country's 28 year wait for a male Olympic swimming champion, finished fourth.

In his delight at winning, Sun took off his swimming cap and attempted to throw it to Chinese supporters in the crowd above him, but it landed in the pool and he had to retrieve it.

It was not his first misstep of a controversial week that has seen a splashing incident in training escalate into a battle conducted via the media between him and his Australian rivals.

A Chinese state newspaper described Australia as “uncivilized” and “Britain’s offshore prison” as it rushed to Sun’s defence after he was labelled a drugs cheat by Australian 400 freestyle gold medallist Mack Horton.

Sun was revealed two years ago to have secretly served a three-month suspension for using a banned stimulant.

He said it was medication to treat a heart issue and did not enhance performance.

Controversial Russian Yulia Efimova had to settle for silver in the women’s 100m breaststroke final .

Lilly King of the United States won gold in an Olympic record of 1:04.93.

Efimova, who has been booed at the pool after her late challenge to be included in the Games despite being initially banned by the International Olympic Committee, finished in 1:05.50. USA's Katie Meili took bronze in 1:05.69.

Defending champion Ruta Meilutyte, the Lithuanian based in Plymouth, was seventh in 1:07.32.

Katinka Hosszu of Hungary won the women's 100 metres backstroke to claim her second gold of the Rio Games, edging out Kathleen Baker of the United States.

Canada's Kylie Masse and China's Fu Yuanhui tied for bronze, with the top four separated by just 0.31 seconds.

Australian world champion Emily Seebohm, swimming in an outside lane, set the early pace but Hosszu powered her way through the field in the last half of the race to touch the wall in 58.45 seconds.

Baker, who qualified fastest for the final, clocked 58.75, to finish a hundredth of a second ahead of Masse and Fu.

It was a second gold in Rio for Hosszu, the self-styled ‘Iron Lady’ of swimming, after her world record-breaking victory in the 400 individual medley on Saturday.

The 27-year-old, who is also in the 200 backstroke, butterfly and medley, had come away empty-handed from three previous Olympics, despite winning five world championships titles.

Seebohm, silver medallist in London in 2012, had achieved the second-fastest time in the heats but qualified for the final in seventh.

She faded in the closing stages on Monday to finish seventh.

Missy Franklin of the United States, the 2012 Olympic champion at 100m, was reduced to a spectator, having failed to qualify in the event for Rio at the US trials.

Franklin was in tears earlier after failing to make the final of the 200 freestyle, but has another chance in the 200 backstroke, in which she also won gold in London.

Ryan Murphy won the men's 100 metres backstroke gold to extend the US run of domination in the event to six successive Games dating back to Atlanta in 1996.

China's Xu Jiayu took the silver and David Plummer, making his Games debut at the age of 30, the bronze for the United States.

Murphy's winning time of 51.97 seconds was an Olympic record and just outside the world record of 51.94 set by compatriot Aaron Peirsol in 2009 when non-textile bodysuits were allowed.