A mysterious "master" has been beating elite Go players online, leading some to suspect that it may actually be a top-level computer.

Until recently, even the best AI programs have struggled to beat the world's top Go players－that is until March when a program called AlphaGo beat South Korean Lee Se-dol, one of the world's best.

However, a player registered with an ID of "Master" on Chinese online board game platforms eweiqi.com and foxwq.com has won 45 fast-paced online matches since Dec 29 against a group of elite Go players, including Lee's compatriot Park Jung-hwan, Japan's Iyama Yuta and China's top player Ke Jie, triggering interest in its identity within the professional Go circle.

No individual player or AI developer has so far claimed to be playing as Master.

Originating in ancient China, Go is a game where two players take turns placing black and white stones on a 19-by-19 grid. Players win by taking control of the most territory on the board, achieved by surrounding opponent's pieces with their own.

The fast-paced format adopted online requires each of the contenders to make at least three moves every 20 seconds.

Yu Bin, head coach of China's national Go team, said the unidentified player's invincible patterns and speed in taking a move almost every five seconds raise suspicions of an AI program at work.

"From its consecutive victories against the world's top human players in such overwhelming fashion, we can rule out the possibility that 'Master' is controlled by a person. It's highly possible that it's the latest version of an AI player," Yu was quoted as saying by Xinhua News Agency.

In March, AlphaGo, which was designed by British AI developer Google DeepMind, defeated Lee－the current world No 8 on GoRatings' world ranking－4-1 in a best of five battle, causing a sensation around the world.

Hua Xueming, leader of China's national Go squad, also followed the winning streak of the virtual player.

"Human players expose their weakness in emotional swings, but it seems this player doesn't. Its approach doesn't fit human patterns, but works reasonably within the rules of the game. I think it might be a newly-developed computer algorithm," Hua said on Tuesday.

China's world No 1 player Ke, 19, who was confident of outplaying AlphaGo after its victory over Lee, has reassessed the strength of AI-powered Go players.

"I couldn't fall asleep last night as I kept thinking about the strength of computers. All the patterns that human players developed over thousands of years have become vulnerable against computers. From now on, human players should study the patterns of computer programs in more depth and improve to a new level," Ke said on his micro blog account.

Gu Li, another elite player from China, offered a reward of 100,000 yuan ($14,300) to the first human player to defeat Master.

"It's not about money. It's about protecting the cultural treasure invented by our ancestors," Gu said on his micro blog account.