Lionel Messi's sublime double gave Barcelona a 2-0 win over Real Madrid in a tempestuous Champions League semi-final first leg which saw Real finish the game with 10 men and with coach Jose Mourinho in the stands.

Messi's two goals settled a scrappy and tense affair at the Bernabeu and gave Barcelona a huge advantage to take back to the Nou Camp.

The Argentine met Ibrahim Afellay's low cross from the right to steer past Iker Casillas from close range 14 minutes from time to break the deadlock.

Messi then netted a wonderful second three minutes from time when he weaved his way into the Real penalty area and slotted past Casillas to give the Catalan side a two-goal cushion to take into Tuesday's return back in Barcelona.

Mourinho was sent off for his protestations soon after midfielder Pepe was dismissed in the 61st minute by referee Wolfgang Stark for a flying tackle on Daniel Alves.

Tempers had already flared at halftime with players and officials involved in a melee near the tunnel.

Barcelona reserve goalkeeper Jose Manuel Pinto was sent off for his part in an unsightly fracas.

A confrontation between Barca midfielder Seydou Keita and Real defender Alvaro Arbeloa as they left the pitch appeared to spark the trouble, which was quickly ended by security staff and police.

The Real fans turned the giant arena into a sea of white flags before kickoff, while several thousand Barca faithful waving Catalan banners high up in the stands tried to make themselves heard above the din.

Real tore into Barca and stopped them playing in the first half of last week's King's Cup final but it was a different story on Wednesday as the visitors dominated possession without showing too much ambition in attack.

David Villa cut in from the right wing in the 11th minute and sent a low drive whistling past the post and Messi sent Xavi clear in the 25th but his effort was straight at Casillas.

The home side's best effort of the first half came moments before the break when Cristiano Ronaldo tested Victor Valdes with a swerving effort the Barca keeper just managed to block.

The second half was short on the kind of attacking football Real and Barca normally produce as the visitors again controlled the ball without ever really threatening the home goal until Messi broke the deadlock and then gave Barca a huge boost for the return leg at the Nou Camp next Tuesday with his second.