Romelu Lukaku and Zlatan Ibrahimovic in furious bust-up during Milan derby

Soccer Football - Coppa Italia - Quarter-Final - Inter Milan v AC Milan - San Siro, Milan, Italy - January 26, 2021, AC Milan's Zlatan Ibrahimovic clashes with Inter Milan's Romelu Lukaku [REUTERS/Daniele Mascolo]

Romelu Lukaku and Zlatan Ibrahimovic clashed viciously as emotions spilled over in Inter Milan's Coppa Italia quarter-final with local rivals AC Milan.

The pair butted heads at the end of the first half and Lukaku launched an X-rated outburst in the direction of his former Manchester United teammate.

The Belgian ace was furious and appeared to say "f*** you and your wife" in the Swede's direction after footage had shown the pair clashing, with Ibrahimovic seemingly referring to Lukaku as a "little donkey".

The quarrel continued after the referee showed both players the yellow card and blew the whistle for half-time, with Inter staff forced to hold Lukaku back as the teams made for the tunnel.

The 27-year-old was also heard saying: "He wants to talk about mothers? Son of a b****."

Ibrahimovic, 39, continued his remarkable season by giving Milan the lead in the 31st minute with his 14th goal of the season.

Both players emerged at the start of the second half with the situation having apparently been calmed, but Ibrahimovic lasted just 13 minutes before he received a second yellow and was dismissed for tripping Aleksandar Kolarov.

Soccer Football - Coppa Italia - Quarter Final - Inter Milan v AC Milan - San Siro, Milan, Italy - January 26, 2021 AC Milan's Zlatan Ibrahimovic clashes with Inter Milan's Romelu Lukaku [REUTERS/Daniele Mascolo]

Incredibly, Lukaku then equalised from the penalty spot for Inter after VAR intervened to award the spot-kick for a foul on Nicolo Barella.

The drama kept on coming at San Siro, with the referee seemingly succumbing to injury late in the second half, forcing the fourth official to take over the main officiating duties.

Christian Eriksen went on to secure Inter's progression to the semi-finals with a sublime 97th-minute free-kick after coming off the bench.

The fiery clash between the two Italian giants comes as tensions run especially high between them, with Milan narrowly leading Inter at the summit of Serie A.

The Rossoneri are top of the league on 43 points, two ahead of the Nerazzuri at the midpoint of the season, leaving fourth-placed Juventus' recent dominance of the division at risk.

Ibrahimovic and Lukaku were teammates at Old Trafford during the 2017/18 season and were believed to have a good relationship.

Soccer Football - Coppa Italia - Quarter Final - Inter Milan v AC Milan - San Siro, Milan, Italy - January 26, 2021 AC Milan's Zlatan Ibrahimovic is shown a red card by referee Paolo Valeri [REUTERS/Daniele Mascolo]

United paid £75million to sign Lukaku from Everton in 2017 and he previously claimed he learned a great deal from his veteran teammate.

“Everything I learned from Zlatan was great, from his stories that he told me when he was at Inter, AC Milan, Barcelona and even Ajax, to being on the field working with him, seeing how competitive he was,” Lukaku told United's official website in early 2019.

“I remember one training session. Because we were both strikers, we were never on the same team and, at one point, there was a 50/50 challenge. He went full-on against me!

“That is when I knew this guy wants to compete and this guy wants to fight for his spot. That is why he changed me. It was an eye-opener. The guy had to fight to be in the position he is in.

“So, I learned just to focus, work hard and enjoy it as well. Because he is a guy who you can have a lot fun with as well and having his personality in the dressing room was good.”

But it appears Lukaku's relationship with Ibrahimovic has significantly deteriorated since the pair were pitted against each other at San Siro.