Google's Go-playing machine has scored a second victory against the best human player.

The victory by AlphaGo against South Korea's Lee Sedol, the winner of 18 world championships, puts the machine's owners one victory away from claiming the $1 million prize.

AlphaGo's first win against Mr Lee in Seoul on Wednesday shook the Go-playing world, marking a milestone in the development of artificial intelligence.

Many believed it would take another decade for computers to conquer the ancient Chinese board game, one of the most creative games devised.

After his first loss, Mr Lee said he was in shock as he did not expect to lose. Google's team compared AlphaGo's win to landing on the moon.

Three remaining games run until Tuesday.

If AlphaGo wins, the prize money is to be donated to Unicef, Go organisations and charities.

Hundreds of thousands of South Koreans, even those who do not play the popular board game, are following the games on live TV and YouTube. All major local newspapers reported Mr Lee's loss on their front pages.

"Two-year-old artificial intelligence masters 5,000-year-old human Go," said a headline in Chosun Ilbo, South Korea's most circulated daily newspaper.