Real Madrid came from behind to beat Real Sociedad 2-1 and climb back to the top of La Liga on Sunday, maintaining their perfect start to the season.

Propelled by the electric Takefusa Kubo, Real Sociedad took an early lead through Ander Barrenetxea, but Madrid hit back with goals from Fede Valverde and Joselu to earn their fifth win from five games.

England international Jude Bellingham was unable to continue his excellent goalscoring form, after netting five goals in his first four Madrid matches, but remains the division's top goalscorer.

Madrid start their Champions League campaign on Wednesday at home against Union Berlin, and despite losing Ballon d'Or winner Karim Benzema in the summer and star player Vinicius Junior to injury, remain a force to be reckoned with.

"We started by letting in a goal and the good thing is that we were capable of turning it around -- the bad thing is that we have to avoid that," said Ancelotti.

"We did it thanks to the commitment, energy and will of the team, we have an intensity that opponents find hard to cope with for 90 minutes."

The Basque visitors went ahead at the new-look Santiago Bernabeu after only five minutes, when Kubo stroked a fine pass into Barrenetxea's path.

Kepa Arrizabalaga kept out his first effort with a fine save but could not claw out the second.

Kubo then beat the goalkeeper with a brilliant strike but it was disallowed for offside.

Joselu hit the crossbar with the goal gaping and Alex Remiro denied Dani Carvajal as Madrid found their footing.

Valverde slammed Real Madrid level less than a minute into the second half, lashing Fran Garcia's cut-back in off the post from outside the area.

The left-back created the second goal too, crossing for target man Joselu to nod the hosts ahead at the back post.

Spain international Joselu was immediately taken off for Eduardo Camavinga, as Ancelotti sought more control of the game.

The Italian got it too, with the visitors effectively shut down, no longer finding spaces between Madrid lines.

"This is the Bernabeu and with our fans we turned it around," said Joselu.

"We're doing a bit of everything, we're confident in ourselves, there's a lot of quality in the squad and we came from behind again."

Madrid lead Barcelona by two points, with both of Spain's giants unbeaten, although the Catalans drew their opening game against Getafe.