ROME - Barcelona beat AC Milan 3-2 at San Siro on Wednesday to secure the top spot of their Champions League group.

Barcelona Lionel Messi celebrates with his teammates after scoring against AC Milan during their Champions League Group H soccer match at San Siro stadium in Milan November 23, 2011. [Photo/Agencies]

The hosts equalised twice through Zlatan Ibrahimovic and Kevin-Prince Boateng after Barca had twice led through Mark van Bommel's own goal and Lionel Messi's 31st-minute penalty.

But Pep Guardiola's side wrapped up a commendable win through Xavi's finish just after the hour mark as Barca, who like Milan had already qualified for the last 16, ensured top spot with a game to spare.

"We are happier compared to the last game," Guardiola said after the thrilling game, referring to their 2-2 draw at the Camp Nou.

"Coming here to San Siro to win and putting in a performance like this was not easy. It's always a pleasure to play in this stadium, especially against Milan, who are one of the most successful clubs in the world," he said.

His Milan counterpart Massimiliano Allegri also took much pride from his side's performance.

"I think it was important for us to play a game like this, facing this team with open football to see what level we are at," he said.

"We leave this match with a defeat, perhaps deservedly, but with greater self-confidence than before. Barcelona played for 95 minutes the way they always do, while we created many dangers for them," he said.

Barca went in front after 14 minutes when Seydou Keita sent in a low ball from the left, Milan midfielder Van Bommel could only divert the ball into the far corner.

Robinho should have equalised in the 19th minute when, after superb work by Ibrahimovic and Boateng, he spooned his first-time effort over Victor Valdes' bar from close range.

The leveller did come moments later. Clarence Seedorf found himself with space on the left and when Ibrahimovic made the run, he found his team-mate with a cute short pass with the outside of his boot. Ibrahimovic made no mistake, nicking the ball under Valdes to put his side level.

Messi hit the bar in the 22nd minute when he beat his marker to Fabregas' low cross from the right but hit his shot off the top of the bar.

Barca were in front again soon after and in somewhat controversial circumstances. Fabregas' lovely ball put Xavi in on goal only for the midfielder to be bundled over by midfielder Alberto Aquilani with referee Wolfgang Stark awarding the spot-kick.

Messi converted the initial kick but was booked and made to take it again after a stuttering run-up foxed Christian Abbiati and he also scored at the second time of asking.

Boateng had a 38th minute effort saved by Valdes when he volleyed Aquilani's diagonal ball at goal.

Boateng put Milan level once more early in the second half, taking a loose ball in his stride majestically before blasting it past the bemused Valdes.

Barca took the lead for a third time in the 63rd minute as Messi dissected the Milan defence with knife-like precision to as Xavi timed his run perfectly to prod home.