Ajax forward Dusan Tadic celebrates scoring against PAOK on Tuesday in Amsterdam, the Netherlands. Photo: VCG

Former European Cup winners had mixed fortunes in Champions League qualifying as Ajax Amsterdam and Red Star Belgrade squeezed into the playoff round while Celtic and Porto were eliminated after a dramatic evening on Tuesday.

Ajax, semifinalists last season, came from behind to beat PAOK 3-2 for a 5-4 aggregate win over the Greeks while Red Star knocked out FC Copenhagen on penalties after a shootout involving 22 spot kicks.

Krasnodar sprung a major upset with a 3-2 win at Porto to advance on away goals after losing the home leg 1-0 and Romania's Cluj won 4-3 at Celtic to eliminate the Scottish champions 5-4 on aggregate.

Ajax youth academy reject Diego Biseswar fired PAOK ahead with a thumping shot at the Johan Cruyff Arena before Dusan Tadic, having had a penalty saved, equalized with another one before halftime.

PAOK keeper Alexandros Paschalakis pulled off a string of superb saves but was undone by a Nicolas Tagliafico header and another Tadic penalty before Biseswar set up a tense finish with a stoppage-time effort.

Richmond Boakye fired Red Star ahead in Copenhagen and Dame N'Doye leveled to force the shootout in which the Danish champions missed two chances to progress before they were dumped out by visiting keeper Milan Borjan.

Borjan kept Red Star afloat with two stops and netted a spot kick himself before he sent the away fans into raptures when he blocked Jonas Wind's weak effort to send the Serbians through.

Having earned a 1-1 draw in Romania, Celtic rallied from an early deficit to lead 3-2 before a late collapse gifted Cluj two late goals and a 5-4 aggregate win over the 1967 champions.

Billel Ormani scored for Cluj after they trailed 2-1 and 3-2 and George Tucudean delivered the final blow in stoppage time as Celtic threw men forward.

Porto fell 3-0 behind to Krasnodar in a dire first half for the Portuguese side as Magomed Suleymanov struck twice after Tonny Vilhena had leveled the tie on aggregate.

The hosts, who have won Europe's premier club competition twice, hit back in the second half through Ze Luis and Luis Diaz but the Russian visitors held on at the Dragao stadium.

Dynamo Kiev looked like overturning a 1-0 first-leg deficit against Club Bruges after Vitaliy Buyalskiy netted early on but the Belgian side hit back.

Stoppage-time substitute Lois Openda silenced the home crowd in Kiev barely a minute after coming on, scoring in the 96th minute to secure a 3-3 draw and book Bruges a playoff clash with Austrians LASK.

LASK followed up their 2-1 win at Basel with a 3-1 home victory over the Swiss team, while Dinamo Zagreb thumped Ferencvaros 4-0 away after a 1-1 home draw with the Hungarians.

Rosenborg beat Maribor 3-1 for a 6-2 overall win over the Slovenians, APOEL won 2-0 at Qarabag to overturn a 2-1 home defeat and Olympiakos Piraeus beat Istanbul Basaksehir 2-0 for a 3-0 aggregate triumph over the Turkish side.