Real Madrid's Cristiano Ronaldo walks on the pitch with the ball under his jersey after their Champions League Group B soccer match against Galatasaray at Turk Telekom Arena in Istanbul September 17, 2013. [Photo/Agencies]

Cristiano Ronaldo underlined his status as Real Madrid's conductor with a hat-trick as they joined holders Bayern Munich and Manchester United in posting big wins as the Champions League group stage started on Tuesday.

Thirty goals rained in around Europe but the Portuguese forward stole the show with a scintillating display in Real's 6-1 hammering of Galatasaray as they began their quest for a 10th European crown with a powerful statement of intent.

Gareth Bale, Real's 100 million euros ($133.49 million)signing, had the honour of becoming the world's most expensive substitute but the Welshman belatedly joined the party to set up Ronaldo's second goal in a one-sided Group B match.

It was Ronaldo's second Champions League hat-trick after his treble against Ajax Amsterdam last year.

Less than four months after a last-minute Arjen Robben goal won last season's trophy for Bayern Munich the Bundesliga giants were quick off the mark in their defence of the title.

David Alaba's powerful early free kick sent Bayern on their way to a 3-0 victory over CSKA Moscow in Pep Guardiola's first European tie since taking charge. Dutchman Robben was on target again with Mario Mandzukic scoring Bayern's other goal.