The Belgian striker, 26, rounded the goalkeeper late on to put Inter back in front with his first Champions League goal for the Serie A side.

He also made Inter's other two goals for Lautaro Martinez; Tomas Soucek had equalised with a first-half penalty.

Inter are in the second qualification spot in Group F with one game left.

The Italians are level on points with Borussia Dortmund, but have a better head-to-head record.

It means Inter, who host group leaders Barcelona on 10 December, will qualify if they at least match Dortmund's result at home to Slavia.

Lukaku, who now has 198 club goals and 52 for Belgium, also had two goals disallowed in the Czech Republic.

Inter's club record signing cut back for Martinez to open the scoring before his team-mate returned the favour, only for the video assistant referee to rule there had been a foul at the other end moments earlier.

Slavia were awarded a penalty for a trip on Peter Olayinka by Stefan de Vrij and captain Soucek sidefooted the spot-kick down the middle past the outstretched leg of Samir Handanovic.

Inter hit the crossbar twice in four minutes after the break, through Lukaku's 65th-minute header and a 25-yard volley by Marcelo Brozovic.

But the Italian outfit restored their lead as Martinez let Valentino Lazaro's through-ball run and defender Michal Frydrych slipped, allowing Lukaku to run through on goal before taking the ball round Ondrej Kolar and firing into an empty net.

Soucek almost equalised moments later as he sidefooted wide from close range following a free-kick but Inter sealed victory as Lukaku delivered a superb cross with the outside of his left foot for Martinez to volley home.

Lukaku thought he had scored again with a low shot in stoppage time but the goal was ruled out for offside.