Lokeren says defender Gregory Mertens died on Thursday, three days after he suffered heart failure during a training match.

The club in Belgium's top division said, "With sadness, we announce the passing of Gregory Mertens."

The 24-year-old player collapsed early in Monday's game, and was kept in a coma.

Lokeren said doctors tried to operate on the player on Tuesday, but there were more complications.

Lokeren said Mertens was medically screened several times during his career, and that nothing pointed toward a fundamental heart problem.