Barcelona's Lionel Messi (R) and Athletic Bilbao's Javi Martinez fight for the ball during their Spanish first division soccer match at San Mames stadium in Bilbao Nov 6, 2011. [Photo/Agencies]

Lionel Messi scored a last-minute equaliser to grab a 2-2 draw for Barcelona at Athletic Bilbao in a dramatic La Liga clash at a rain-soaked San Mames on Sunday.

Cristiano Ronaldo struck a hat-trick as Real Madrid crushed Osasuna 7-1 and Jose Mourinho's team lead the standings on 28 points, three ahead of the European and Spanish champions.

The clash between Barcelona coach Pep Guardiola and Argentine Marcelo Bielsa had been eagerly anticipated and produced a breathless encounter in Bilbao.

Barca keeper Victor Valdes was beaten for the first time in 10 matches when Ander Herrera fired Bilbao in front in the 20th minute, but Cesc Fabregas headed the visitors level just four minutes later.

Standing water on the pitch added to the tension and the conditions contributed to both late goals.

A Bilbao corner 10 minutes from time was cleared badly by Eric Abidal and the ball rebounded off Fernando Llorente and then Gerard Pique before slipping past Valdes.

In the frantic closing minutes Bilbao's Fernando Amorebieta was sent off for a second yellow card and Barca grabbed an equaliser after a free kick, which pinged around the area until it fell to Messi to score his 14th this season.

"We have shown a lot of character and maintained our unbeaten start," Fabregas told Spanish television. "It was a very difficult match especially in the second half with such a wet pitch.

"It was typical match at San Mames against a team with a great spirit and fantastic fans."