Wales came desperately close to snatching an unlikely point against Belgium, but were condemned to defeat in Brussels and are at serious risk of relegation.
Kevin De Bruyne tortured the Dragons in a testing first half, opening the scoring with a perfectly placed first-time effort after 11 minutes.
The Manchester City star then teed up Michy Batshuayi for a tap-in just before the interval to give Rob Page's men a mountain to climb in the second half.
But hope was not lost for Wales as Brennan Johnson weaved his way through the channel and picked out Kieffer Moore with a teasing cross, and the Bournemouth striker pulled one back for the visitors.
Gareth Bale emerged from the bench and nearly headed Wales level not long after, before Belgium were awarded a penalty when De Bruyne fell under a challenge from Joe Morrell. However, the referee overturned this after a VAR intervention as the Portsmouth midfielder had clearly won the ball.
Johnson came close to firing in a Wales equaliser as stoppage time loomed, while Roberto Martinez was sent off just before the final whistle.
Belgium sit three points behind the Netherlands, while Wales are the same margin off of Poland.