Google's DeepMind AlphaGo program saw off South Korea's Go master, Lee Sedol, in the first of five matches between the computer and a human professional player. Lee conceded defeat - in what experts said was a close match - after three and a half hours, when it became clear that AlphaGo had taken an unassailable lead.

"We landed on the moon," Demis Hassabis, chief executive and co-founder of Google subsidiary DeepMind, which built AlphaGo, said in a tweet after the victory against the professional player. "So proud of the team!"

Shock defeat

Lee, who holds 18 Go titles to his name and is widely considered one of the modern era's best players of the ancient Asian game, reacted with some surprise after his loss.

"I didn't think AlphaGo would play the game in such a perfect manner," he said after the match, which drew in tens of thousands of viewers on YouTube. "I would like to express my respect to the program makers for making such an amazing program."

It is not the first time that a computer has outsmarted a human at Go. In October 2015, AlphaGo beat the European champion, in a victory which was not expected for years. Lee however, was considered a far more challenging opponent.

The Lee versus AlphaGo match series continues over the coming days. Both sides are competing for around $1 million (910,000 euros) in prize money, which Google says it will give to charity if it wins.

hch/hg (AFP, AP, Reuters)