The fourth-seeded Czech, twice a winner in Gstaad, was outplayed by claycourt specialist Montanes in the opening set before he took control to complete his 12th straight victory in the event.

Novak, who beat Wimbledon [ Images ] champion Roger Federer [ Images ] in last year's final, won the title for the first time in 2001.

"I struggled in the first set but was more aggressive in the second," said Novak. "In the third, I was really focused."

Novak will play Potito Starace in the quarter-finals after the unseeded Italian beat Romanian Victor Hanescu 3-6, 7-6, 7-6.

Russian Igor Andreev defeated 1999 tournament winner and eighth seed Albert Costa of Spain 6-2, 6-4 to book his place in the last eight.

Also Read Federer eases into second round of Swiss Open

Costa, the 2002 French Open [ Images ] champion, had no answer for Andreev's accurate serving and powerful ground strokes.

The Russian will meet Ruben Ramirez Hidalgo, for a place in the semi-finals, after the Spaniard beat Austrian Stefan Koubek 6-3, 6-4.