Media playback is unsupported on your device Media caption USA's King grabs gold from Russia's Efimova

US swimmer Lilly King has stirred Olympic waters when she called out Russia's Yulia Efimova over a doping scandal with a single gesture.

The 19-year-old, who claimed a gold medal over Ms Efimova in the 100-metre breaststroke on Monday, incited a reaction reminiscent of the Cold War online, with users roasting the Russian in a series of patriotic and finger-wagging memes.

The gesture was in response to a back-and-forth row between the pair, which began when Ms Efimova, who had twice failed drug tests, was cleared of a doping ban and allowed to compete just before the breaststroke event.

The decision was derided by her Olympic competitors and drew ire from crowd members, who booed the Russian during the event.

Old divisions

Ms Efimova, 24, won her semi-final heat on Saturday and held up her index finger to suggest number one.

In response, Ms King wagged her own finger in disapproval while watching on a television monitor, a gesture they would continue to direct at one another throughout the event, culminating with Ms King's gold win.

But the heated exchange recalled old divisions marked by the former Iron Curtain, with Americans hailing Ms King as a hero and painting Ms Efimova as a villain.

Image copyright Twitter

Image copyright Twitter

Image copyright Twitter

Other swimmers shared their frustrations over Ms Efimova's appearance.

Swedish swimmer Jennie Johansson wrote on Instagram: ""Unfortunately I finished up 9th. My heart and my mind will still be swimming in that final tomorrow even if the actual lane is taken by someone that doesn't deserve it."

"Cheaters are cheaters," said Irish swimmer Fiona Doyle, who missed out on the semi-finals by one place.

Ms King also did not back down, saying after she won: "It's incredible, winning the gold medal and knowing I did it clean."

Ms Efimova hit back at her critics, saying athletes should rise above politics.

"I always thought the cold war was long in the past. Why start it again, by using sport?" she said, according to Russia's Tass agency in Rio.

Hero at home

Image copyright Reuters Image caption Ms Efimova was lauded as a hero on Russian social media

In Russia media, however, Ms Efimova's silver medal was praised as "more precious than gold" and the athlete described as a hero.

State TV channels and mainstream newspapers suggested that Ms Efimova prevailed after overcoming both the initial ban for doping allegations and her American opponent's taunts.

"What she had to go through in addition to attempts not to let her compete at Rio can be seen in this video: minutes ahead of her appearing on the lane, US [swimmer Lilly] King, standing behind Yulia, all but frowned", State-owned Rossiya 1 said, according to a BBC translation.

NTV, owned by Russia's gas giant Gazprom, also highlighted Ms King's "nonsportslike" behaviour.

Social media users and Russian bloggers on Facebook largely defended Ms Efimova, directing criticisms at US athletes such as Michael Phelps, who lauded his teammate, Ms King, for calling out the doping scandal.

Russia's Yulia Efimova beaten to gold by Lilly King of USA

Yulia Efimova and the 'fog of suspicion'

"Let Efimova alone, she's to compete yet, and you've stirred a storm," Facebook user Zoya Kudryasheva said.

She added: "Heroes may be forgiven for some things".

The Russian Embassy in the Netherlands made reference to the showdown in a Tweet, congratulating Ms Efimova on her "silver medal with the golden tint".

Other Russian users expressed pride over Ms Efimova's silver medal, with one user tweeting: "Winning a medal at these dirty Olympics is a sporting feat!"

Another Twitter user said: "She's a beauty with nerves made of steel, a very strong personality. At a time like this, silver is worth its weight in gold."

Revelations from a damning report earlier this year found that Russia's sports ministry manipulated urine samples provided by its athletes between 2011 and 2015.

The International Olympic Committee allowed 271 of the nation's athletes to compete from the original entry list of 389, despite calls for a total ban on the country by the World Anti-Doping Agency.