Lionel Messi proved a thorn in Arsenal's side yet again as his second-half goals earned Barcelona a 2-0 win at Arsenal in the first leg of their Champions League last 16 tie.

The Spanish holders' feared attack had been well shackled by a disciplined home side for much of the evening, but a lightning break after 71 minutes saw Argentine Messi teed up by Neymar to score past keeper Petr Cech for the first time in his career.

Messi, who scored four goals against the Gunners in 2010 and a double a year later in knockout round wins, doubled Barca's lead seven minutes from time when he beat Cech with a penalty, having been tripped by Arsenal substitute Mathieu Flamini.

Arsenal relied on counter-attacks and had chances, most notably from Alex Oxlade-Chamberlain and Olivier Giroud, but now have a daunting task to turn the tie around in the Nou Camp.