The trickle of Asian footballers heading to Europe has grown into a steady stream in recent years, with players like Japan's Hidetoshi Nakata, South Korea's Park Ji-Sung and Iranian Mehdi Mahdavikia leading the way.

Yet the trend of European clubs snapping up players from the region in the hope of exploiting lucrative foreign markets is a growing concern to Asian Football Confederation (AFC) officials.

Speaking ahead of Saturday's kick-off in the 16-team Asian Cup continental championship, AFC general secretary Peter Velappan said his organisation was keen for players to try their luck overseas.

"The best leagues are in Europe," Velappan told AFP. "We encourage our young players to try and go to these clubs in Europe to understand what it means to be a professional footballer and to improve their mental strength."

But Velappan said European clubs often signed Asian stars primarily for commercial reasons, hampering players' development.

"Some of these mega-clubs have been coming to Japan and China in particular, only for commercial reasons," Velappan said.

"The players are signed by a club and then loaned out to clubs in other countries, they are just using these players for their own ends.

"We're not talking about a lot of clubs here but this is a trend that we need to be very vigilant against," Velappan added.

Although he did not name clubs and players involved, Velappan appeared to be taking a swipe at English Premiership giants Manchester United, who signed Chinese youngster Dong Fangzhou earlier this year.

Dong, who signed from Chinese side Dalian Shide, had barely set foot inside Old Trafford before he was whisked off on loan to Belgian side Royal Antwerp.

He has yet to play in a senior game for Manchester United but is likely to be called up whenever United tours around football-mad Asia, where the club enjoys phenomenal support.

Velappan said young players being courted by European teams should only join if there was a solid development structure.

"We would like many of our Asian players to go to Europe, but ideally they should go there at junior level and become part of the club's academy where there is a clear structure leading to youth teams and then reserves," he said.

The Asian Cup gets underway in Beijing on Saturday, with hosts China meeting Gulf side Bahrain.