Inter Milan struck late to beat Slavia Prague 3-1 on Wednesday and stay in contention for a place in the Champions League round of 16 after a free-flowing game featuring many chances.
The two swapped roles in the 35th minute, but the video referee disallowed Lukaku's effort because of a foul.
Tomas Soucek levelled for Slavia but Inter sealed victory in the last 10 minutes when Lukaku shot into an empty net after his marker slipped, allowing the Belgian striker to score his first Champions League goal of the season.
Martinez sealed victory for the Italian side in the 89th minute.
Barcelona lead Group F on 11 points after beating Borussia Dortmund 3-1 and have qualified for the last 16. Inter and Dortmund are level on seven points with Slavia bottom on two.