Cristiano Ronaldo scored his third hat-trick in four games as he helped Portugal beat Armenia 3-2 in Yerevan on Saturday.
Armenia, who are bottom of the Group I standings, took a surprise lead in the 14th minute when Marcos Pizzelli found the back of the net from a free-kick, but Ronaldo levelled matters from the penalty spot in the 28th minute.
The Real Madrid ace put Portugal ahead in the 55th minute after some sloppy defending from Robert Arzumanyan allowed him to steal the ball with keeper Roman Berezovsky stranded.
Ronaldo grabbed his third in world class fashion, surging towards goal before unleashing a thunderbolt into the top corner.
Hrayr Mkoyan scored with 18 minutes to go to set up a nervy finish for Portugal, who had seen Tiago Cardoso sent off, but the visitors held out for the win.
Elsewhere in Group I, Denmark claimed a key 2-0 victory over Serbia to ensure they remained in second behind Portugal.
Yussuf Poulsen opened the scoring for the Danes after 13 minutes, with Jakob Poulsen doubling Denmark's advantage in the second half.
Andre Schurrle scored a hat-trick as Germany thumped Gibraltar 7-0 in a Group D encounter. Gibraltar had done well to limit Germany to just one goal in the opening 45 minutes, with Bastian Schweinsteiger having a penalty saved, but the floodgates opened in the second half.
Schurrle completed his hat-trick, while Max Kruse scored a brace and Ilkay Gundogan and Karim Bellarabi also got on the scoresheets as the World Champions ran riot.
However, the result was not enough to take them to the top of Group D, with Poland retaining top spot after a 4-0 victory over Georgia.
Robert Lewandowski scored a hat-trick in the last four minutes of the match to give the scoreline a commanding look to it after Georgia had battled valiantly throughout.
In the final match in Group D, the Republic of Ireland and Scotland played out a 1-1 draw in Dublin. Jonathan Walters opened the scoring for the Republic in the 38th minute, before Scotland drew level shortly after the half-time break when Shaun Maloney's effort deflected in off of John O'Shea.
In Group F action, leaders Romania were held to a goalless draw by second-placed Northern Ireland in Belfast. It's the host who will feel they could have grabbed the victory, with Kyle Lafferty and Oliver Norwood missing chances late on.
An 82nd-minute effort from Zoltan Stieber helped Hungary to a 1-0 win over Finland in Helsinki. The victory sees Hungary tighten their grip on third place in Group F, and they are now just two points behind Northern Island.
Greece's horror campaign continued as they were defeated 2-1 by Faroe Islands. A goal in each half from Hallur Hansson and Brandur Olsen gave Faroe Islands the ascendancy, with Socratis Papaststhopoulos' late goal proving to be nothing more than a consolation for the Greeks.