Norwegian grandmaster Magnus Carlsen retained his world chess title on Friday as he recorded a fourth win over Russian challenger Ian Nepomniachtchi.

Carlsen sealed victory by winning the 11th game of the 14-game series in their two-million-euro ($2.3 million) match in Dubai.

Nepomniachtchi resigned with a brief handshake and the two players exchanged a few words.

Carlsen, who turned 31 during the competition, has now won five world titles in a row, taking the first in 2013.

The contest in Dubai started with five draws before the Norwegian won the longest game ever played at a world championships at nearly eight hours to unlock the contest.

Carlsen exploited mis-steps by his opponent to win games eight and nine. Then, as black in Friday's game 11, pounced on more inaccuracies by the Russian to retain the title 7.5-3.5 with three games still to play.

As winner he collects 60 per cent of the 2 millon dollar (1.77m euro) prize fund.

"It's hard to feel that great joy when the situation was so comfortable to begin with, but I'm happy with a very good performance overall," Carlsen told the post-match press conference.

He said his marathon first win was pivotal.

"Game six decided everything," Carlsen said.

"After five games there were five draws and I had very few chances to play for anything more. Then everything kind of clicked and it all went my way."

The two men had been rivals since the 2002 under-12 championship when Carlsen cracked in his final game against English youngster David Howell to hand Nepomniachtchi, who is slightly more than four months older, the title.

Carlsen has called the set-back "one of my worst memories in chess."

Entering the world championship, and excluding draws, the Russian had a 4-1 edge over the Norwegian in matches in the traditional long format, but in Dubai Nepomniachtchi cracked.

"You don't expect necessarily to run away with it in a world championship," Carlsen said. "That's fine by me."

Nepomniachtchi implied one of his problem was nerves.

"Experience is never easy. It should be tough to gain some real experience. It was a little bit too much here," he said.

"The tension is not a reason to overlook some simple things you would never ever overlook in a blitz game," he added.

"In my career I lost some stupid games, but not as many in such a short time."

- 'Cope with the moment' -

Carlsen sympathised.

"He couldn't show his best chess, which is a pity for the excitement in the match," he said. "Sometimes it happens when your get in a difficult situation. All the preparation doesn't help if you can't cope in the moment."

On Friday, Nepomniachtchi miscalculated in a pawn endgame and resigned following move 49 after Carlsen had queened a pawn and it became clear the Russian would not be able to do the same.

Carlsen said that in the later stages of the match he had been able to wait for his opponent to make errors.

"A lot of my decisions skewed conservative and, with hindsight, it worked quite well," Carlsen said.

Besides the world title, Carlsen has topped the points classification for more than a decade and has an encyclopedic knowledge of his discipline.

He founded the Play Magnus brand, which includes an eponymous application and online chess platforms, and raised nearly 40 million euros ($49 million) when it was floated on the Oslo Stock Exchange in October 2020.

In September, he won the Norway Chess competition featuring six top players including Nepomniachtchi. The two met twice, playing out two long draws followed by two wins for Carlsen with tie-breakers.