Ajax, semi-finalists 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 bizarre shootout involving 22 spot-kicks.
Azeri champions Qarabag took a big step towards the playoff round with a 2-1 win at Cypriot side APOEL but Dinamo Zagreb left their progress hanging in the balance after the Croats played out a 1-1 home draw against Hungary's Ferencvaros.
Neymar made his return to the pitch after a three-month injury lay-off as Paris St Germain celebrated their eighth Ligue 1 title with a 3-1 win against Monaco at the Parc des Princes on Sunday.