Two-time world chess champion Magnus Carlsen won his third title on Wednesday, defeating Russian challenger Sergey Karjakin after three weeks of grueling play in the World Chess Championship

Fans greeted the Norwegian with a "happy birthday" chorus and huge cheers after his victory. He turned 26 on the same day he beat the Russian, winning two of four tie-breaking "rapid games."

The grandmasters started Wednesday's chessboard battle with a 6-6 tie after 12 games. They will share a prize of $1.1 million, the winner getting 60 per cent.

Organisers say about 6 million people around the world followed the series of quick tie-breaking games — similar to sudden death play in football.

If none had ended with a winner, the championship would have gone to the nerve-wracking Armageddon endgame, which lasts less than 10 minutes.

Hungarian grandmaster Judit Polgar, the commentator for the tournament and the best ever female player, calls it "the killer 10 minutes — like Russian roulette."

For the final throes of this endurance test, hundreds of spectators streamed into a refurbished lower Manhattan building that once was the city's fish market.

The match would have gone to an Armageddon endgame if Carlsen hadn't won (Getty)

Some stood behind a soundproof glass pane watching the two men facing off at the chessboard, with a lineup of water bottles keeping them hydrated.

To guard their concentration, the competitors could not see through the glass.

Outside, men, women and children speaking dozens of languages got a close-up view of the action on screens set up in a lounge overlooking the Brooklyn Bridge.

"Magnus is my hero because he takes risks, he's really exciting," said Pippa Millstone, a Manhattan nine-year-old who came to watch the tournament for her fourth time.

Carlsen won two of four tie-breaking 'rapid' games to claim his third title (Getty)

As she and two other children played their own game on a coffee table, the stars hovered above them on a giant screen.

"The game is pretty even now," the girl said, "but I feel like Magnus is going to start attacking really soon."

And the 25-year-old Norwegian did just that — during the second half of the third "rapid" game.

Spectators paid $100 to watch the play, and $500 for VIP seats close to the players behind the glass, plus lounge space with snacks and drinks.

But most fans were in homes and clubs across the globe. Some spent $15 for a Pay-Per-View live transmission, others watched using high-tech goggles in 3D virtual reality or by tracking moves on various free websites.

The World Chess Championship took place in New York (Getty)

The first two of four games of "rapid chess" both ended in draws after two hours — compared to championship games that can last as many as six hours or more.

The New York championship did not escape the shadow of East-West rivalry reaching back to the Cold War days when American Bobby Fischer beat Russian Boris Spassky in 1972.

This time, a key figure in chess was absent in New York: Kirsan Ilyumzhinov, a Russian businessman and longtime president of the governing World Chess Federation who was accused by the U.S. government of collaborating with the Syrian regime and barred from visiting.