By Jeb Blount

RIO DE JANEIRO (Reuters) - France's Charline Picon claimed Olympic gold in the women's RS:X sailboard competition in a fiercely contested medal race that pushed Italy's Flavia Tartaglini, the leader before the medal round, out of the podium positions.

With only six points separating the top six of 10 sailors qualified for the medal round after 12 preliminary races, the gold, silver and bronze were mathematically attainable by most of the final-round sailboarders.

Sailed in nearly perfect firm and lightly shifting winds, the test allowed Picon to jump from fourth overall to the top of the podium in one of the closest and most dramatic Olympic medal round races ever.

China's Chen Peina won silver and Russia's Stefaniya Elfutina took bronze. Standing third and second before the medal race they had to fight from behind to survive.

Chen used impressive downwind power to grind back from a poor start and sixth position at the upwind gate. Her third-place finish left her two points shy of gold.

Elfutina, at 19 the youngest sailor at the Games and Russian's first sailing medalist in 20 years, made the first mark in last place after taking a penalty turn.

"I stopped thinking about my position there," she said. "The only thing I could do was pump."

The pumping, a board sailing action where the sailor repeatedly pulls and eases back the sail to drive the bard forward, worked.

She finished seventh, enough to edge out World Sailing's No. 2-ranked RS:X sailor Lilian de Geus of the Netherlands, by a single point.

By passing Tartaglini, helping push her into eighth, Elfutina essentially pushed the Italian out of the podium spots.

The men's RS:X medal race took place under sunny skies and in near perfect sailing conditions just off Rio's Flamingo beach before several thousand ardent fans. Two of the three medals, though, had already been wrapped up on points before the start.

Showing up was all Dutchman Dorian van Rijsselberghe had to do to clinch gold and Britain's Nick Dempsey to claim silver.

Only the bronze was at stake and France's Pierre le Coq, fourth overall going into the final, was able to sneak onto the podium with a seventh-place medal-race finish.

In the men's Finn heavy single-person dinghy, Giles Scott, four-time world champion in the class, guaranteed Britain's second sailing medal of the Games on points after 10 preliminary races, World Sailing said.

Even if Scott finishes last in the medal race on Tuesday, he is assured of the gold medal.

(Reporting by Jeb Blount; editing by Ken Ferris)