Brussels - Belgium under-21 international Gregory Mertens died on Thursday, three days after collapsing with heart failure during a match, a spokesman for his club, Sporting Lokeren, said.
The 24-year-old defender had been in a coma since going into cardiac arrest early in a reserve team game on Monday.
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Club spokesman Herman Van De Putte told Reuters that his condition continued to worsen and the player's family had agreed with doctors to switch off the life support system.
"With sadness we announce the loss of Gregory Mertens," Lokeren said on its Twitter feed. "We wish family and friends all strength."
Mertens, who joined top flight Lokeren last summer after nearly 100 appearances for Cercle Brugge, collapsed 15 minutes into the game at KRC Genk and despite lengthy efforts to bring him round doctors quickly said his survival needed a "miracle".
His death shocked many across European soccer.
"Shockingly sad," tweeted former England striker and television presenter Gary Lineker.
Manchester City said on Twitter: "Our thoughts are with the friends and family of @KSCLokeren's Gregory Mertens at this sad time."