Captain Thierry Henry opened the score line in the 38th minute before Alexander Hleb sealed the comfortable victory three minutes after re-start as the Gunners notched their second victory in the group stage.

Arsenal's win put them in top spot on six points, leading CSKA Moscow, who edged rooted Hamburg 1-0, with two points while Porto lie third on one point.

The home side dominated the game from the starting whistle and had the opener denied in the second minute when Kolo Toure's goal was disallowed as Cesc Fabregas crossed the backline before crossing to the Ivorian international.

Robin Van Persie tested Porto goalkeeper Helton twice with two powerful shots but the Brazilian remained in control.

But Helton was beaten shortly after when Henry headed into the side netting after connecting with a first-time cross from Emmanuel Eboue.

Henry turned provider in the 48th minute when he laid the ball off to the daring Hleb who drilled a low drive past a fully-stretched Helton.

Earlier in Moscow, Dudu scored just before the hour mark to give CSKA an important 1-0 win over Hamburg.

The Brazilian eluded his marker to head a Daniel Carvalho corner-kick past the goalkeeper in the 59th minute.

Hamburg's crisis deepened five minutes from time when substitute Benjamin Lauth was shown a straight red card for elbowing Dudu during an aerial challenge.

The television replay proved the challenge to be normal.