Barcelona set up a Champions League quarter-final against Bayern Munich after overcoming Napoli on a night of high VAR drama at the Nou Camp.
Quique Setien's hosts scored three times through Clement Lenglet, Lionel Messi and Luis Suarez in an incident-packed first half, during which Messi was also denied a second for handball.
With the tie evenly poised at 1-1 after February's first leg, Messi produced a mazy run and sublime finish to double his side's lead on the night following Lenglet's headed opener.
The Argentine had a possible second disallowed by VAR for handball but was later awarded a penalty by the video referee after being brought down by Kalidou Koulibaly, allowing Luis Suarez to step up to make it 3-0 on the night.
The first-half drama was not over there, as Ivan Rakitic conceded a penalty for a foul on Mertens and Lorenzo Insigne converted for Napoli in the fifth minute of injury time.
In a significantly quieter second period, Lorenzo Insigne failed to test Marc-Andre ter Stegen with a header as the visitors chased a lifeline, while substitute Arkadiusz Milik was on the pitch for less than two minutes when he saw a goal ruled out for offside in the closing stages.
German champions Bayern Munich await Barca in the last eight after beating Chelsea 4-1 on Saturday to complete a 7-1 aggregate victory.
"This was the first forward step we wanted and now it is to be hoped we play the matches in front of us with the same attitude which we demonstrated here," Barcelona manager Quique Setien said.
"The team played well and we deserved this. All the rivals who are left are strong and there are only complicated matches left. It will be tough for us but for Bayern too. They're a great side but so are we."
BDST: 1322 HRS, AUG 09, 2020