Barcelona manager Hansi Flick was upset over several refereeing decisions in his side's 4-3 loss at Inter Milan that stopped the Catalans reaching their first Champions League final in a decade after an extra-time winner by home substitute Davide Frattesi.

Barca thought it had victory in the bag, when it roared back from two goals down to grab a 3-2 lead with Raphinha's goal in the 87th minute, but Inter equalized late through Francesco Acerbi to stay alive, before grabbing a winner in extra time.

"I'm proud of my team, we gave everything, and sometimes it's like that," Flick told reporters.

"We have to accept it, and we start again next season.

"To win the Champions League, this is one of our goals. We will be back next season."

Flick criticized Polish referee Szymon Marciniak who had a busy night in the semifinal second leg at the San Siro, with Inter advancing 7-6 on aggregate to face either Paris St Germain or Arsenal.

He awarded Inter a penalty after a VAR review for a challenge by Pau Cubarsi on Lautaro Martinez that he did not deem an infringement, and later reversed a decision he had signaled as a spot kick for Barcelona, with VAR saying Henrikh Mkhitaryan's foul on Lamine Yamal was just outside the box.

Barca's players and bench also complained about what they thought was handball inside the box by Inter defender Acerbi, and a foul by fullback Denzel Dumfries on Gerard Martin in the build-up to the equalizer, which took the game to extra time.

"I don't want to talk too much about the referee, but every decision that was 50-50 went (Inter's) way," Flick told a news conference.

"I am disappointed, but not with my team. They tried everything. It's the way it is. We are out, but next year, we will try again to make the fans happy.

"It makes me sad. My team did an excellent job. I've told (Marciniak) what I think, but I'm not going to say here what I said."

Barca was chasing a treble after winning the Copa del Rey, but will now turn its focus to La Liga, where it tops the table and on Sunday hosts rival Real Madrid, which Barca leads by four points with four games to go.

The five-time winner was hoping to reach its first Champions League final in a decade, but was left licking its wounds ahead of the final scheduled "Clasico" of the season on Sunday.

"And of course, La Liga, it will be also a tough match on Sunday, but we will also give everything," added Flick.

"When (the players) look in the mirror when they arrive at home at three or four o'clock in the morning, I think they can be very proud."

Unbeaten domestically since late December, Barcelona will try to grab a fourth consecutive victory over Real this season.

"We'll learn from this. It's a progression. We want to keep learning. We don't have much time to train now, but next weekend we are back. It's normal to be disappointed," Flick said.

"The team deserves the respect they have earned.

"We play to win, we want to win titles and we have La Liga, with a very difficult match. We have a few days to prepare for it.

"We'll analyze tonight's game calmly and see what we can do."

Agencies