The last-32 2nd leg was played behind closed doors at the San Siro due to the fact of the danger of coronavirus.
Cauly opened the scoring for the Bulgarian side, before Cristiano Biraghi and Lukaku put Inter 2-1 up.
The Ludogorets players and staff arrived at the stadium carrying medical face masks, as they had completed on the way to their lodge on Wednesday, and have been 2-0 down from the first leg in opposition to Antonio Conte’s men.
Brazilian midfielder Cauly put the visitors in the front on 26 minutes with his first goal for the club to level the tie, preserving off Diego Godin’s challenge to score off the underside of the bar.
Six minutes later it was once all square as former Tottenham man Christian Eriksen sent a through ball to Biraghi to squeeze in at the close to post.
On the stroke of half-time Lukaku gave Inter a 2-1 lead – not that the Belgian knew an awful lot about it.
Former Manchester United team-mate Alexis Sanchez fed the ball into Lukaku, whose initial header was saved by Ludogorets goalkeeper Plamen Iliev, but the ball rebounded on to the striker’s head and found its way into the net.
Authorities have validated greater than 300 cases of coronavirus and 12 deaths in Italy, with the outbreak centered on a small cluster of towns in the northern Lombardy and Veneto regions.
Inter were one of four Serie A clubs to put off their game closing weekend with extra league matches affected this weekend.
Manager Conte stated the Italian giants did well regardless of the lack of followers inside the famous stadium.
“It seemed like a training session, playing behind closed doorways created a very peculiar atmosphere,” stated Conte.
“The lads did well to put matters back in place without delay after we suffered the goal.”