United, who started with Wayne Rooney on the bench, completely dominated the opening period and wasted half a dozen chances to take the lead.

Inter goalkeeper Julio Cesar denied Cristiano Ronaldo on three occasions while Ryan Giggs also came close as Sir Alex Ferguson's side did not allow Jose Mourinho's troops a look-in.

Inter came back strongly in the second half, however, and might have snatched victory late on when Esteban Cambiasso spurned a glorious opening in front of the United goal after failing to make a telling connection with Zlatan Ibrahimovic's flick.

Ronaldo might had won the game with the very last kick of the match but Julio Cesar did just enough to keep the Portuguese winger's free-kick at bay.

Barcelona came from behind to snatch a crucial away goal in a 1-1 draw against Lyon at Stade Gerland.

Lyon went ahead after just seven minutes when Juninho netted with a superb trademark free-kick over the head of the out-of-position Victor Valdes.

Barca claimed the equaliser after 67 minutes when Xavi's corner was flicked on by Rafael Marquez and Thierry Henry finished off the move with a header at the far post.

Arsenal will take a slender lead into the return leg at the Olympic Stadium against Roma after claiming a 1-0 victory at the Emirates.

Robin van Persie scored Arsenal's winner, the Dutchman converting from the penalty spot in the 37th minute after being brought down in the box by Philippe Mexes.

Emmanuel Eboue had a glorious chance to extend the Gunners' advantage after the break but somehow fired wide after doing all the hard work to get in a position just eight yards from goal.

Porto goalkeeper Helton was let off the hook as his side recovered from his first-half howler to claim a 2-2 draw at Atletico Madrid.

Maxi Rodriguez's third minute opener for the hosts was cancelled out by Lisandro Lopez's leveller midway through the half, but Atletico were gifted the lead again on the stroke of the break when a Diego Forlan shot slipped through the grasp of Helton and into the net.

Lisandro pulled the scores level again in the 72nd minute as the 2004 European champions came away from the Vicente Calderon much the happier of the two teams.