Spain and Serbia are on the verge of qualifying for the 2018 World Cup in Russia after wins on Tuesday, while Croatia and Iceland are top of a very tight Group I.
Spain followed up Saturday's 3-0 win over Italy by crushing liechtenstein 8-0 to remain top of Group G, three points ahead of the Azzurri, who labored to a 1-0 win over Israel.
Serbia is similarly in control of Group D after beating Ireland 1-0 to go four points clear.
Matters are far less clear in Group I, where four teams are separated by just two points with two games left.
Group leader Croatia and Iceland have 16 points, while Turkey and Ukraine are both just two points behind.
Only the nine group winners automatically advance from European qualifying, with the eight best runners-up going to a playoff round.
GROUP D
A goal from Aleksandar Kolarov guided 10-man Serbia to a 1-0 win over Ireland, putting the Balkan nation on the verge of a place at next year's World Cup.
The win in Dublin leaves Serbia top of the group, four points clear of Wales with two games remaining against Austria and Georgia.
17-year-old liverpool player Ben Woodburn came on as a substitute. Aaron Ramsey made it 2-0 for Wales deep into stoppage time.
Austria drew 1-1 at home to Georgia.
GROUP G
Alvaro Morata and Iago Aspas each scored two goals as Spain maintained its three-point advantage over second-placed Italy with two matches remaining.
Spain also scored through Sergio Ramos, Francisco "Isco" Alarcon, David Silva and an own goal by Max Goeppel as it repeated its 8-0 victory over liechtenstein last year and guaranteed itself of at least second place in the group.
Spain has a much better goal difference than Italy so it can virtually secure first place with a home win against Albania in Alicante on October 6.
Italy is all but assured of a spot in the playoffs as Ciro Immobile's second-half goal means the Azzurri need just one point from their final two qualifying matches to secure second spot and a playoff berth. It next plays Macedonia in Turin on October 6, three days before it visits Albania.
GROUP I
Cenk Tosun scored a second-half goal to lead Turkey to a 1-0 win over Croatia that blew the group wide open.
Group leader Croatia and Iceland have 16 points each, while Turkey and Ukraine are both just two points further back.
Tosun slammed the ball home in the 75th minute after Croatia goalkeeper Danijel Subasic was unable to hold on to a fierce drive by Oguzhan Ozyakyup at a packed stadium in Eskisehir.
Iceland recovered from Saturday's 1-0 loss to Finland to beat Ukraine 2-0, thanks to two second-half goals from Gylfi Sigurdsson.
Finland beat Kosovo 1-0 in a match between the two bottom teams. Teemu Pukki's late goal handed Kosovo its seventh straight defeat in its first major qualifying competition.