But Barcelona were stunned when Ruben Castro fired a free-kick past Raul Bravo to level after a Sergio Busquets foul had presented him with the opportunity.
City led when Aguero converted from the spot - despite missing two penalties on Tuesday - with his second deftly nodded in from Kevin de Bruyne's free-kick.
Juan Mata curled in a free-kick with five minutes to go, before Ashley Young's set-piece was bundled into his own net by Juventus defender Alex Sandro.
The Spanish government pledged to stop a poll declared illegal on a day of violent protests and unrest. Barca took the decision to play behind closed doors 25 minutes before kick-off, with thousands of fans outside.
Theo Walcott fired in the first goal for the Gunners in the 31st minute moments after missing a penalty. Philippe Coutinho pulled one back with a brilliant free-kick before Adam Lallana fired in after the break.
Inter Miami outdueled Nashville SC in a penalty kick shootout 10-9. Messi scored in the 23rd minute. Nashville's Fafá Picault scored in the 57th minute.
There were emotional scenes before kick-off as both sets of supporters paid tribute to former Spurs boss Terry Venables, whose death at the age of 80 was announced on Sunday.
Dele Alli added a second with a low finish inside the area following a clever ball from Son Heung-min. Spurs were awarded a penalty when Alli was brought down by Fernandinho but Bravo saved Erik Lamela's spot-kick.
Liverpool twice took the lead in a thrilling first half, but Fulham responded on both occasions. Alexander-Arnold's stunning free-kick went in off Bernd Leno (20) but Harry Wilson (24) brought the visitors level.
Fresh from his 1995 EP which dropped in December, Kida Kudz kick-starts 2015 with the viral video for his widely accepted single – Tooto! Tooto is the first song off the EP, Produced by HOD & the video was shot in Bodija, Ibadan!
Prince Handsome who recently clinched the award for EU BEST REGGAE DANCE HALL ACT (NEU AWARDS 2014) is not ready to take it slow as he kick-starts his 2015 campaign with this brilliant piece titled "I'm Sorry" produced by TrashMark and Video
Mikel Merino, Mikel Oyarzabal and Ander Barrenetxea scored, and Brais Mendez missed a penalty kick, for Sociedad in the first 21 minutes of the game, while in the second half Rafa Silva netted Benfica's first goal in the competition after three
The match took place 90 minutes after Buckingham Palace confirmed the passing of Her Majesty the Queen at the age of 96. A minute's silence was observed ahead of kick-off, with both sets of players wearing black armbands.
David de Gea made a string of good saves as Liverpool dominated, with the away side managing just one shot on target. The second leg is at Old Trafford on Thursday, 17 March (20:05 GMT kick-off).