Already trailing 2-0 in Novi Sad, Gareth struck a free-kick from 30 yards that swerved wickedly in the air from right to left, leaving home goalkeeper Vladimir Stojkovic helpless.
The goal should have offered Wales hope but they conceded again in the 39th minute to trail 3-1 at half-time and then fell to a 6-1 defeat in the second half. Gareth played the full 90 minutes.
Staying in Group A, Jan Vertonghen and Mousa Dembele both started as Belgium came from 1-0 down to draw 1-1 against Croatia in Brussells. Jan played 90 minutes, Mousa was replaced by Kevin de Bruyne in the 72nd minute.
Jermain Defoe also played 90 minutes and had a goal disallowed in the first half as Frank Lampard scored a late equaliser for England to rescue a point against Ukraine in Group H. Kyle Walker and Jake Livermore remained on the bench at Wembley.
Gylfi Sigurdsson and Iceland's fine start with a win against Norway on Friday was dented somewhat by a 1-0 loss in Cyprus in Group E. Konstantinos Makridis hit the winner in Larnaca in the 57th minute. Gylfi played the full match.
Hugo Lloris captained France again as they made it two wins out of two in Group I with a 3-1 success against Belarus at the Stade de France.
In CONCACAF qualifying, Clint Dempsey played 90 minutes as the USA moved back to the top of their group with a 1-0 win against Jamaica in Columbus, Ohio.