Ramsey slots home second from Ozil through ball
Mkhitaryan's first goal for Arsenal with shot across keeper
Return leg takes place in London on 15 March
One back for Borussia Dortmund through Andre Schurrle at home to Red Bull Salzburg.
And we have a goal in Moscow as Marcelo puts Lyon ahead against CSKA.
Atletico Madrid 2-0 Lokomotiv Moscow
Borussia Dortmund 1-2 Red Bull Salzburg
CSKA Moscow 0-1 Lyon
AC Milan 0-2 Arsenal
Giacomo Bonaventura slips as he takes the free-kick and it's into the wall.
AC Milan 0-2 Arsenal
Aaron Ramsey concedes a free-kick with a high foot on Lucas Biglia - except it's not that high. Yellow card. Dangerous position.
AC Milan 0-2 Arsenal
AC Milan bring on £34m summer signing Andre Silva - all eight of his Milan goals this season have come in the Europa League.
Patrick Cutrone, the club's top scorer this season, is replaced.
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Ed O'Toole: AC who? Italian Serie A isn't what it used to be. Juventus scraped through last night and Arsenal and Milan are both similarly placed in respective leagues.....
Melvyn Jacobs: Have the Arsenal team kissed and made up? Four losing games on the trot because they hated the sight of each other, and now!
Laurence Malt: Even if Arsenal win tonight it still demonstrates an inconsistency which Wenger seems incapable of preventing.
AC Milan 0-2 Arsenal
Arsenal defender Ainsley Maitland-Niles does well to track Suso and deny him a chance to cross.
It goes out for a corner, which is half-cleared to Ricardo Rodriguez, whose shot flies wide.
AC Milan 0-2 Arsenal
Milan have a lot of work if they are to extend their 13-game unbeaten run. But they've only had one shot on target. It's been a disappointing game for Gennaro Gattuso's side so far.
But the Gunners are looking in good shape to end this four-game losing run.
Image source, Getty ImagesAC Milan 0-2 Arsenal
Milan sub Nikola Kalinic latches onto a long ball but good strong defending by Shkodran Mustafi takes the ball off him and the Gunners defender wins a free-kick off the striker.
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The worst thing for Arsenal is always the uncertainty - City had Pep confirmed as manager months before he was due to start - Arsenal need to do the same this summer even if Arsene does stay one more year.
Nigel, Kent
Amazing how some people, even Arsenal "supporters" just can't stop sniping. Is it too much to ask you to support your team? Even when they're winning and playing better, you look to criticise and to find fault. Pathetic.
Tony J
I have an idea for a debate - Mkhitarian or Sanchez? I think Mkhitarian as his passing is far better and he generally has a more positive effect on the team.
Alex Maynard
AC Milan 0-2 Arsenal
Not great news for Arsenal as left-back Sead Kolasinac limps off to be replaced by England Under-21 utility man Ainsley Maitland-Niles.
Milan also make a change - striker Nikola Kalinic, once of Blackburn, replaces playmaker Hakan Calhanoglu - so that's two up front now for Milan.
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Daniel Cheng: This is all good lads but too late into the season for us to start playing football. Even if we win it its still not good enough.
Adrian Li: Anyone else see this as Gattuso's ploy to keep Wenger in a job and ruin Arsenal's next season?
Alphonse Rawlinson: Are you really an Arsenal fan if you are willing them to lose just to get rid of Wenger? They say the passion has gone from the Premier League...They may be right.
AC Milan 0-2 Arsenal
Is Giacomo Bonaventura on some kind of long-range goal bonus for this second half? He has another lash from distance - driving over the bar again.
Now Arsenal defender Sead Kolasinac is booked for handball, although the ball flicked up onto his arm. A bit harsh.
AC Milan 0-2 Arsenal
Sead Kolasinac plays a one-two with Henrikh Mkhitaryan but then the Arsenal left-back's cross is past everyone in the centre.
The other three games are a few minutes ahead of the San Siro as they reach the hour mark.
Diego Costa with a second for Atletico Madrid and two for Valon Berisha in the second half for Red Bull Salzburg in Dortmund.
Still goalless in Moscow.
Atletico Madrid 2-0 Lokomotiv Moscow
Borussia Dortmund 0-2 Red Bull Salzburg
CSKA Moscow 0-0 Lyon
AC Milan 0-2 Arsenal
Giacomo Bonaventura has his third chance of the second half but this 20-yard effort is deflected out for a corner. Better from Milan since the break I'd say. They're edging play at the moment.
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Bibek: We have the players and today they are showing what they are capable of. But still Wenger needs to go..
Hiroyuki Sato: As much as I’d love to see Arsenal’s success, I’d rather not see this year’s Arsenal winning the Europa League as the board as well as the manager will be content with the result and won’t make any change.
Max Talavera: Arsenal 2-0 away at AC Milan and their fans complain. Sometimes perspective and self awareness is truly lacking in football.
AC Milan 0-2 Arsenal
A Milan player takes a foul throw-in and manager Gennaro Gattuso is highly animated about it on the sideline.
I imagine Gattuso being similarly passionate about everything. "What do you mean we've run out of ketchup?"
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AC Milan should be grateful they are only playing Arsenal and not Brighton.
Tony, Wimbledon
AC Milan are having a similar season on the domestic league front to Arsenal. Best to not get carried away!
Rob
Don't forget... it's a tie of four quarters, and Arsenal have only won one so far.
David, London
AC Milan 0-2 Arsenal
Another chance for Milan - and it's Giacomo Bonaventura again. Davide Calabria puts in a low cross from the right which finds Jack near the penalty spot. He has time and space but he leans back and sends it well over the bar.
AC Milan 0-2 Arsenal
Milan midfielder Giacomo Bonaventura, known as Jack in Italy, cuts in from the right but his low shot is saved by David Ospina at his near post.