Barcelona took the lead in the 21st minute through Ronaldinho's penalty-kick but fellow Brazilian Ronaldo equalized nine minutes from the break.

The guests played with 10 men since the 24th minute after veteran Brazilian defender Roberto Carlos was shown a straight red card for a vocal protest over refereeing.

The victory preserved Barca's 11-point lead at the top of the league and moved them closer to retaining their title.

Barcelona started as the absolute favorites and almost broke the deadlock in the 4th minute when Ronaldinho released Mark Van Bommel with a long ball but the Dutchman chipped just wide.

Ronaldinho and Samuel Eto'o made two attempts shortly after but Real keeper Iker Casillas had no problems.

In the 21st minute, Carlos clipped Van Bommel who cut inside the area and the referee awarded Barca a spot kick.

Ronaldinho stepped up and thundered a low shot into the left corner leaving Casillas diving into the opposite direction.

Three minutes later, Carlos, who lost his tempers since the goal, vocally protested a free-kick near the area only for the referee to hand up a straight red card.

Real Madrid leveled against the run of the play when Ronaldo latched on to a def through pass from Julio Baptista, outpaced marker Motta and chipped the ball past advancing keeper Casillas.

Barcelona, who play Benfica on Tuesday in the second leg of the Champions League quarter-finals, lost both full backs Motta and captain Carles Puyol who were pulled off the pitch due to different injuries.