Paris Saint-Germain and Schalke wrapped up the top spots in their Champions League groups Tuesday, and Cristiano Ronaldo scored his tournament-leading sixth goal to help Real Madrid beat Ajax 4-1.

A 17-minute snow delay during the Dinamo Zagreb-Dynamo Kiev match offered something unexpected on a night when all places in the last 16 were decided before kickoff.

Kaka also scored for Madrid, but Borussia Dortmund won the group earlier by beating winless Manchester City 1-0. Borussia Dortmund will be seeded in the Dec. 20 draw.

PSG beat pre-match leader FC Porto 2-1 to top Group A. Last-place Zagreb scored its first goal and first point of the campaign in a 1-1 draw with Kiev.

Arsenal lost 2-1 at Olympiakos, allowing Schalke to win Group B despite drawing 1-1 with Montpellier.

Malaga had already clinched Group C before drawing 2-2 with Anderlecht, and second-place AC Milan lost 1-0 at home to Zenit St. Petersburg.

Madrid and Milan are dangerous unseeded teams in a well-balanced knockout stage beginning in February. Teams cannot be paired with anyone from their home country, or an opponent they already faced in the groups.

Ajax and Zenit join Kiev and Olympiakos as the third-place teams entering the last 32 of the Europa League. That draw also is Dec. 20.

Ronaldo finished an excellent attack in the 13th minute that was started by Luka Modric’s strong tackle in his own half and his long diagonal pass that sent Karim Benzema clear of the Ajax offside trap.

The Portugal winger’s goal-a-game ratio in the group stage moved him clear of Lionel Messi, Burak Yilmaz and Alan, who each have five goals but could all play Wednesday.

Modric set up Jose Callejon for the first of his two goals in the 28th. Callejon added a header in the 88th off Alvaro Morata’s cross.

In between, Kaka curled in a perfectly placed left-foot shot from 25 yards in the 49th to give Madrid a 3-0 lead.

Ajax scored in the 59th when Derk Boerrigter volleyed into an unguarded net after backup goalkeeper Antonio Adan had weakly punched the ball out of his penalty area.

Dortmund, which was drawn into the toughest pool as the lowest-ranked team, sealed its group win against the underachieving English champions. Julian Schieber scored in the 57th, sliding between defenders to connect with Jakub Blaszczykowski’s pass at the far post.

Under pressure in the French league, PSG justified some of the massive spending of its Qatari owners with a tournament-best fifth win thanks to two offseason signings from Italian clubs.

Brazilian defender Thiago Silva, formerly of Milan, headed the Paris side ahead in the 29th, and former Napoli forward Ezequiel Lavezzi scored a fortunate goal when his shot slipped through goalkeeper Helton’s grasp in the 61st. Jackson Martinez headed Porto level in the 33rd.

In Croatia, play was stopped early in the first half during a snowstorm. Colored pitch markings were painted during the delay and play restarted with an orange ball.

Andriy Yarmolenko gave Kiev a 45th-minute lead, but Zagreb leveled deep into second-half stoppage time when substitute Ivan Krstanovic scored from the penalty spot. The draw ended Zagreb’s run of 11 straight group-stage defeats, stretching to September 2011. (AP)