South Korean Go player Lee Se-dol (right) places the first stone against Google’s AlphaGo, as Google DeepMind’s lead programmer Aja Huang observes, during a match in Seoul on Wednesday. [Photo/Agencies]

Google's computer program AlphaGo defeated its human opponent, South Korean Go champion Lee Se-dol, on Wednesday in the first game of a historic five-game match between human and computer.

AlphaGo's victory in the ancient Chinese board game, also known as weiqi, is a breakthrough for artificial intelligence, showing the program developed by Google DeepMind has mastered one of the most creative and complex games ever devised.

Commentators said the game was close. The result was unpredictable until near the end. Lee's loss was a shock to Go fans.

"A mistake I made at the very beginning lasted until the very last," said Lee, 33, who has won 18 world championships since becoming a professional Go player at the age of 12.

Lee said AlphaGo's strategy was "excellent" from the beginning. Yoo Chang-hyuk, another South Korean Go master, described the result as a big shock.

Hundreds of thousands of people watched the game live on TV and YouTube. The remaining four games will be played by Tuesday.

Computers conquered chess in 1997 in a match between IBM's Deep Blue and chess champion Garry Kasparov, leaving Go as "the only game left above chess", Demis Hassabis, Google DeepMind's CEO, said before the game.