Manchester United have become embroiled in a Chinese match-fixing case after a referee admitted taking a bribe to fix the coin toss in a friendly against Shenzhen FC.

Leading Chinese referee Huang Junjie has admitted that he received money in relation to a 2009 match between Sydney FC and China's Shanghai Shenhua, and to United's 6-0 friendly win over Shenzhen FC in 2007.

Huang, named on a three-man shortlist for China's referee of the year in 2009, admitted accepting over £160,000 in bribes to fix the international and domestic matches. The clubs involved are not thought to have been aware of any suspicious activity.

Manchester United admitted their surprise last night when told of the case.

"We had been unaware of this until now, but if there are any questions to be asked, then we are waiting to be contacted," said a United spokesman.

"We do not expect to hear anything, however."

Twenty former officials and referees are scheduled to face the courts as part of a crackdown on corruption in Chinese football.