Bayern's stunning start to the standout quarter-final between the only past champions in the last eight saw Thomas Muller score twice and Ivan Perisic and Serge Gnabry add on in the first half hour.

Barcelona conceded eight for the first time since 1946 after Joshua Kimmich, Robert Lewandowski and Philippe Coutinho (twice) piled on in the second half.

Barcelona tallied only seven shots on target in the whole game, getting on the board with an own-goal by David Alaba in the first half and through Luis Suarez in the second.

"It's a disastrous result. An embarrassment," Barcelona defender Gerard Pique said. "This, today, is unacceptable."

Seeking their first title since 2013, Bayern will next face either Manchester City or Lyon, who meet on Saturday in the last quarter-final.

Paris Saint-Germain and Leipzig are in the other semi-final of the mini-tournament being staged without fans in Lisbon amid the coronavirus pandemic.

"Brutal," Kimmich said. "It's hard to comprehend beating Barcelona 8-2. We were so focused from the first minute, we wanted to get forward with intent. An incredible result in the end, but we're not done yet."

Bayern's biggest victory in Champions League history kept alive their quest for a sixth title, which would move them ahead of Barcelona. The German club has the most wins against Barcelona in the tournament's history.

"We knew that if we put them under pressure, we would get chances," Bayern coach Hansi Flick said. "We have such quality and intensity in this team, now we need to recharge and focus on the next game, where we start again from zero."

The humbling loss ended a forgettable season for Barcelona, one that included a coaching change and public disputes between players and team officials.

It is the first time since 2008 the club has finished a season without a significant title. They haven't lifted the European trophy since 2015.

Quique Setien's remaining time as coach is expected to be counted in hours. He was already under fire after Barcelona relinquished the Spanish league lead - and title - to Real Madrid after the competition resumed following the pandemic break.

"Right now it's too soon to be talking about whether I stay at the club or not," Setien said. "The reality is that it doesn't depend on me.

"It's worth all of us working out what's important and considering a wide range of things which correspond to a defeat of this importance and which is so painful."

Coutinho - on loan from Barcelona - closed the scoring with goals in the 85th and 89th minutes and didn't celebrate.

His goals rubbed salt in Barcelona's wounds as they try to offload him.

Barcelona's demise means no Spanish club has reached the semi-finals for the first time since 2007.

Australian Associated Press