Inter Milan starting XI (3-5-2): Sommer, Bisseck (subbed for Darmian), Acerbi, Bastoni, Dumfries (subbed for De Vrij), Barella, Calhanoglu (subbed for Zielinski), Mkhitaryan (subbed for Frattesi), Dimarco (subbed for Carlos Augusto), L.Martinez (subbed for Taremi), Thuram

Bench: Di Gennaro, J.Martinez, Arnautovic, Asllani, Re Cecconi, Zalewski

Goals: Martinez 21’, Calhanoglu 45’ (Pen), Acerbi 90+3’, Frattesi 99’

Barcelona starting XI (4-2-3-1): Szczesny, Garcia (subbed for Fort), Cubarsì (subbed for Pau Victor), Martinez (subbed for Araujo), Martin, De Jong, Pedri (subbed for Gavi), Yamal, Dani Olmo (subbed for Fermin Lopez), Raphinha, Ferran Torres (subbed for Lewandowski)

Bench: Pena, Astralaga, Fati, Christensen, Farré, Darvich

Goals: Garcia 54’, Olmo 60’, Raphina 87’

In the end it took extra time, two astonishing fightbacks and 13 goals to separate Barcelona and Inter and see the Italian team - who were seconds away from elimination - prevail 7-6 on aggregate after winning another roller-coaster encounter 4-3 on Tuesday (Wednesday AEST).

Substitute Davide Frattesi was the extra-time hero for Inter, firing home in the 99th minute to leave the Barcelona players slumped to the ground and all his Nerazzurri teammates - including those on the bench - racing to celebrate with him.

“I don’t know what happened tonight. I’m lucky I managed to finish the game, I screamed so much [in celebration] that I saw everything black,” Frattesi told Italian broadcaster Sky.

Moments earlier, he had been encouraging the already loud San Siro crowd to make more noise, and the atmosphere grew even more feverish after Frattesi delivered on his super-sub reputation again.

“That’s part of my career,” the midfielder said.

“I wasn’t given so much incredible talent, but I am always the last one to give up and the first one to believe we can do it. At 3-3, I told Marcus [Thuram] that we would go through.”

Three-time European champions Inter, who lost the 2023 final to Manchester City, will face either Paris Saint-Germain or Arsenal in Munich on May 31.

PSG beat Arsenal 1-0 in London last week in the first leg of their semi-final. The second leg is on Wednesday (Thursday AEST) in Paris.

There was little sign of the drama to come at halftime, with Inter comfortably leading 2-0 after Lautaro Martinez scored and earned a penalty, which was converted by Hakan Calhanoglu.

But Barcelona had been in that position before, trailing by the same score early in the first leg last week before securing a thrilling 3-3 draw.

And Eric Garcia scored nine minutes after the break, before Dani Olmo headed in the equaliser six minutes later.

Raphina appeared to have secured the win for Barcelona when he put the Spanish side ahead two minutes before full-time, tucking away the rebound after Yann Sommer had saved his initial shot.

However, 37-year-old Francesco Acerbi levelled in stoppage time - his first goal in European competition - to add another 30 minutes to the tantalising encounter.

Frattesi had proved crucial off the substitutes’ bench before, both for Italy and Inter, and so he was again, controlling Mehdi Taremi’s pass and dummying around Pau Cubarsi before curling past Wojciech Szczesny.

Barcelona almost levelled again, but Sommer made a fingertip save to push Lamine Yamal’s shot past his post.

“I said to them (the Barcelona players) I know everyone is disappointed … but at the end we can be proud of our performance,” Barcelona coach Hansi Flick said.

“I’m proud of my team … we have to accept it and we start again next season.”

AAP