SEOUL, March 9 -- Artificial intelligence (AI) unexpectedly defeated the world human champion of the ancient Chinese board game Go in the first of their five-game match held in Seoul on Wednesday, drawing worldwide attention on the human versus machine showdown.

South Korean Lee Sedol, one of the greatest Go players who has topped the world ranking for most of the past decade, was shockingly beaten by AlphaGo, a computer program developed by Google's London-based AI subsidiary DeepMind.

AlphaGo took the world by surprise after beating European Go champion Fan Hui by 5-0 in October last year and even defeated the world champion though four games are left, a result out of widespread expectations among Go experts.

Go enthusiasts had hoped it would take years, or perhaps decades, for AI to triumph over the best human players, but it's now evident that AI technology is much more advanced than many have expected.

The "match of the century" drew great attention from across the world, with hundreds of local and foreign journalists from China, South Korea and Japan as well as the United States and European countries gathering at the Four Seasons hotel in central Seoul.

During a press conference in Seoul a day before the opening match, Lee lowered confidence in his victory as AlphaGo seemed to have improved its intuitive power. Go had been viewed as the last game humans can dominate over AI due to its intuitive nature and complexity.

Demis Hassabis, CEO of the DeepMind, told the press conference on Tuesday that AlphaGo has made many upgrades since the game with Fan Hui in October 2015, based on which many experts predicted Lee's sweep victory.

AlphaGo won the opening match, taking a 1-0 lead in the five-game match that will run through next Tuesday. The next game will be held at the same hotel in Seoul from 1 p.m. (0400 GMT).

Lee and AlphaGo played a tight game by the middle of the match, but the 33-year-old resigned when it became clear that the computer program had taken an unassailable lead.

Playing black, Lee put his first position in the right flower spot, and about one and a half minutes later, AlphaGo placed its first marker in the left flower. One of DeepMind developers put AlphaGo's markers on the board, shown through Internet broadcasting, on behalf of the computer program.

From the very beginning, Lee played anomalously by placing his fourth marker at an irregular position, which a commentator said it was the first anomaly he has ever seen from the South Korean Go professional.

AlphaGo responded "calmly" to the anomaly, playing aggressively to Lee who in turn took counterattacks against the algorithm, the commentator said.

Lee's slight domination by the middle of the match was reversed as AlphaGo infiltrated into the right areas of black put by the human champion. He tried to change the situations in his favor, but he finally admitted his defeat after his 186th placing.

As Lee got the black which allows his faster starter than AlphaGo, Lee had to win 7.5 areas more than AlphaGo as a handicap for victory, according to Chinese Go rules adopted in the match.

Go originated from China more than 2,500 years ago. It involves two players who take turns putting markers on a grid -shaped board to gain more areas on it. One can occupy the markers of the opponent by surrounding the pieces of the other.

To cover the human versus AI fight, hundreds of journalists gathered at the venue from around the world. The match was broadcast live through TVs in South Korea, China and Japan, with Google's YouTube showing it through an Internet live-stream.

Kim Hyun-jin, wife of Lee Sedol, and their daughter Lee Hye-lim who came to the venue to watch Lee's match, were surrounded by lots of local and foreign journalists at the corner of the hotel for interviews while the match was going on.

At the VIP room, South Korean politicians and senior government officials watched the landmark game, including floor leader of ruling Saenuri Party, head of the main opposition Minju Party, Seoul Mayor Park Won-soon and other government officials.

After the announcement of Lee's defeat, people watching the match in and around the venue voiced a sigh over the unexpected loss of the human champion.

Lee has won world Go champions 18 times in the past 11 years, recording a winning rate of about 70 percent with 47 victories in professional matches. AlphaGo has recorded a 99.8 percent winning rate with 504 victories and only one defeat.

With the victory, Google is expected to enjoy great promotional effects from the match of the century, which is also forecast to help Go, known as Weiqi in China and Baduk in South Korea, gain popularity in Western countries as well as in Asia.

The promotion effect is estimated to reach at least 100 million U.S. dollars in consideration of worldwide attention and news media reports from Western countries as well as Asian nations. Google allegedly has invested about 2 million dollars, including 1 million dollars in prize, for the landmark event.

The match drew great attention from news organizations, Go fans and even the general public around the world. With the victory, AlphaGo developer DeepMind could gain reputation as one of the world's leading AI companies.

AlphaGo boasts of its deep learning, a capability of learning to discover new strategies for itself by playing thousands of games between its neural networks and adjusting connections by use of a trial-and-error process known as reinforcement learning.

The world AI market is forecast to grow to nearly 2 trillion dollars by 2025, expanding its application to various fields such as healthcare, disease analysis and even legal advices.

The match between Lee and AlphaGo is also projected to help the Chinese board game gain popularity in Western countries as well as in Asia.

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Lee Sedol says surprised by AlphaGo, expects 50-50 victory

South Korean Lee Sedol, world champion of the ancient Chinese board game Go, said Wednesday that he was "very surprised" by the capability of AlphaGo, developed by Google's London-based artificial intelligence (AI) subsidiary.