Championship leader Fernando Alonso stayed out of the limelight on Friday ahead of a home Spanish Grand Prix that promises another epic battle with Ferrari's Michael Schumacher.

After getting used to empty stands on Friday mornings so far this season, Formula One awoke to Alonsomania at the Circuit de Catalunya.

Opening practice saw thousands of fans filling the main grandstand, a far more impressive turnout than the sparse crowd on race day at what turned out to be a thrilling San Marino Grand Prix at Imola two weeks ago.

Tickets have long been sold out for Sunday's race with Spaniards eager to witness another duel between Alonso, increasingly seen as Schumacher's heir apparent, and the seven-times world champion.

Schumacher is chasing his seventh Spanish Grand Prix victory and a record-equalling fifth in a row at the Barcelona circuit where he has never finished out of the points in 14 appearances.

Renault's Alonso is hoping to become the first Spaniard to win his home race after already becoming the first to lead the championship.

The two men's battle at Imola provided an enthralling contest, Schumacher harrying Alonso all the way to the finish line as the Spaniard held his nerve with a controlled and defensive drive under pressure.