Chelsea's victory at Salzburg earlier on Wednesday (AEDT) gave Stefano Pioli's side the chance to go second in Group E and it grasped that opportunity with both hands.

Gabbia put it in front with a first-half header and they ran away with it in the second half, with Rafael Leao doubling their lead before Olivier Giroud added a third from the penalty spot.

Robert Ljubicic's bizarre own goal summed up Dinamo's night as their hopes of qualifying were emphatically ended, while Milan only need to avoid defeat in a decisive last group match against Salzburg next week to advance.

Simon Kjaer and Charles De Ketelaere had goal-bound shots blocked in a bright start from Milan, before Gabbia came to the rescue by nodding away a Mislav Orsic header that was looping in.

Dominik Livakovic palmed away a Giroud header and Josip Misic did superbly to get in the way of a shot from Ante Rebic that looked to be heading for the back of the net, but the Serie A champions were in front 39 minutes in.

The opening goal came from an unlikely source, as Gabbia punished slack defending by diving to head home a whipped Sandro Tonali free-kick from close range.

Leao gave Milan breathing space five minutes into the second half, showing great pace to drive into the penalty area from the left all too easily and capitalise on more poor defending with a clinical right-foot finish.

Milan was cruising and they had a third goal just before the hour mark, when Ljubicic upended Tonali and Giroud's spot-kick found the top-left corner.

Things went from bad to worse for Ljubicic when Giroud failed to make contact with the livewire Leao's cutback and the ball struck the midfielder on the shoulder before flying into the back of his own net.