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Belgium took full advantage of Croatia's stumble and moved three points clear of Igor Stimac's team at the top of the table.
Kevin de Bruyne, who has been playing at Werder Bremen on loan from Chelsea this season, sent new Blues boss a timely reminder of his qualities when he opened the scoring in the 13th minute against Serbia.
Everton midfielder Marouane Fellaini headed home the second for Belgium on the hour mark in front of staff from Chelsea, as the Daily Mail reported.
Manchester City defender Aleksandar Kolarov scored a late consolation for the Serbs.
If Belgium qualify automatically from Group A, they will owe Robert Snodgrass a credit for his goal in Scotland's 1-0 victory in Croatia.
Ten-man Italy survived with a point from the Czech Republic thanks to veteran goalkeeper Gianluigi Buffon.
AC Milan striker Mario Balotelli was dismissed in the 72nd minute after picking up two yellow cards in four minutes.
But Juventus and Italy captain Buffon, 35, made several fine stops to give his team a four-point lead over second-placed Bulgaria.
Malta earned their first win of the qualification group with a 1-0 victory in Armenia.
LA Galaxy striker Robbie Keane became the Republic of Ireland's most-capped player in his 126th appearance and celebrated with a hat-trick in the 3-0 win over the Faroe Islands in Dublin.
The win moved Giovanni Trapattoni's team level on 11 points with second-placed Austria, who defeated Sweden 2-1 in Vienna.
Germany, however, still hold a five-point advantage at the top of the table.
Group leaders Switzerland left it late to defeat Cyprus in their match in Geneva on Saturday.
Haris Seferovic, who has spent this year on loan to Nevara in Serie B from Fiorentina, struck the only goal of the game in the 90th minute as Ottmar Hitzfeld side extended their lead at the top of the group to four points.
Iceland missed out on the chance to top the group when they were 4-2 by Slovenia in Reykjavik, while Albania were also denied the chance to move above the Swiss by a late Norway equaliser in the 1-1 draw in Tirana.
Helder Postiga gave Portugal a ninth-minute lead against Russia, which they never surrendered, to fire his team back into contention for automatic qualification.
The win lifted Cristiano Ronaldo and his teammates above the second-placed Russians and Israel in the table.
However, Portugal have played two games more than Russia and one more than the Israelis.
At the foot of the group, Azerbaijan and Luxembourg drew 1-1 in Baku to move the home country above Northern Ireland, who are second bottom.
Bosnia-Herzegovina produced a five-goal second-half blitz in Riga to defeat Latvia 5-0.
The win maintained Bosnia's three-point advantage at the top of the group over second-placed Greece, who won 1-0 in Lithuania.
Slovakia, though, were left stunned after only drawing 1-1 against bottom side Liechtenstein.
England were handed a boost as Ukraine ran out 4-0 winners at group leaders Montenegro.
The result means the Montenegrins have now played a game more than Roy Hodgson's team, who are two points behind.
However, Ukraine's big win moved them ominously into third place and a single point behind England ahead of their clash in Kiev on Sept. 10.
But it was a bad night for Poland, who could only draw 1-1 in Moldova, despite Jakub Blaszczykowski opening the scoring in the seventh minute after combining with Borussia Dortmund teammate Robert Lewandowski.