Inter Milan stormed back from three goals down to draw 3-3 away to Benfica after Joao Mario’s first-half hat-trick.

The Portuguese international bagged a brace inside the first 15 minutes and netted a third just after the half-hour mark to put Benfica on course for their first win in the group stages.

Inter Milan, who had already qualified, sparked a second-half fightback when Marko Arnautovic pulled a goal back six minutes after the break before Davide Frattesi’s 58th-minute goal gave the away side more hope.

The comeback was complete with 18 minutes to go when Alexis Sanchez netted a penalty before Antonio Silva saw red late on for Benfica.

The Portuguese side opened the scoring in the fifth minute after a looped ball into the box was headed down by Casper Tengstedt into the path of Mario, who lashed home from close range.

Inter almost had an equaliser five minutes later but Kristjan Asllani’s effort from outside the box was well saved by Anatoliy Trubin.

The hosts doubled their lead in the 15th minute when Tengstedt capitalised on some lazy Inter possession and drilled a low ball into the box which fell nicely for Mario to poke home.

Benfica made it three in the 34th minute and Tengstedt was once again the creator, this time he lifted a ball into the six-yard box and Mario was on hand to pounce and hit the first Champions League hat-trick of his career.

Inter started the second period with much more intent than the first and were denied when Carlos Augusto’s powerful effort was turned behind by Trubin and the Ukrainian shot stopper was on hand to push Sanchez’s free-kick over the crossbar a couple of minutes later.

The away side cut the deficit to two goals in the 51st minute when Yann Aurel Bisseck’s header was pushed into the path of Arnautovic who prodded in from close range.

Inter grabbed their second just before the hour mark when Francesco Acerbi’s cross was wonderfully volleyed home by Frattesi to make it 3-2.

The visitors had a chance to equalise after Marcus Thuram was brought down by Nicolas Otamendi inside the area and Sanchez sent Trubin the wrong way from the resulting spot-kick to dramatically level things up at three apiece.

Benfica almost regained their lead in the 82nd minute after Di Maria’s curling effort from outside the area looked to be heading into the top corner but Emil Audero palmed behind for a corner.

The home side were then reduced to 10 men a couple of minutes later. Antonio Silva lunged in late on Nicolo Barella and his yellow card was upgraded to a red after a VAR check.

Inter had a chance to snatch it late on but Barella’s first-time effort from inside the box was lashed against the post before Trubin held on to Federico Dimarco’s second shot as both sides took a share of the spoils.