By Mark Elkington

MADRID (Reuters) - Lionel Messi took up where he left off last season as the Argentine scored twice to help Barcelona and new coach Tito Vilanova to a 5-1 home win over Real Sociedad in their La Liga opener on Sunday.

Carles Puyol, Pedro and David Villa, who came on for his first competitive action since breaking his leg last December, also scored to give Barca an immediate advantage over arch-rivals Real Madrid who were held 1-1 at home by Valencia.

"It was a good win but the best news of all is the return of 'El Guaje' (Villa), we have missed him," Barca midfielder Xavi told Spanish television.

The champions had earlier dominated at the Bernabeu, but were frustrated by a new-look Valencia and some outstanding saves from goalkeeper Diego Alves.

World Player of the Year Messi scored a league record 50 goals last season and settled Barca with quick strikes to give them a 3-1 lead inside 15 minutes at the Nou Camp.

Pedro volleyed in a fourth just before the break but the biggest cheer was reserved for Spain striker Villa when he was brought on in the second half and then stroked home the fifth goal near the end.

Although it is only the first round of matches, a two-point advantage for Barca over Real is significant because Jose Mourinho's side only dropped 14 in their 38 games last term on their way to a league record points tally of 100.

REAL FRUSTRATED

Earlier, Gonzalo Higuain gave Real a 10th-minute lead from Angel Di Maria's cross and, in stifling temperatures, they comfortably held the visitors at bay until just before the break.

Valencia, sporting a host of new faces, had few ideas going forward but leveled when Jonas headed in from a free kick.

Alves was the visitors' outstanding player in the second half, keeping out a string of efforts as Real upped their game and pressed, but Valencia held firm to help earn a point for their new coach Mauricio Pellegrino.

"I expected more from my team," Mourinho told a news conference. "We haven't played a great game, but we did enough to win."

Up on the north coast, Real Betis overcame Athletic Bilbao at San Mames in an eight-goal thriller.

The visitors were three goals up in 31 minutes before last season's Europa League and King's Cup finalists responded in the second half.

Bilbao's Oscar De Marcos got a goal back just after the break and Mikel San Jose then struck twice to level the scores with 14 minutes to go before Betis finally triumphed late on through Alejandro Pozuelo and Jorge Molina with his second.

(Editing by Tim Hart)