Cristiano Ronaldo took his goal tally for the season to 53 in 51 games for club and country as he scored twice in Portugal's 3-0 win over Latvia in Riga.

The Real Madrid ace also laid on an assist for Andre Silva to seal the World Cup qualifying victory for the Selecao, keeping them three points adrift of Switzerland at the top of Group B.

Portugal were made to work hard in the first half but stepped things up in the second, and they did more than enough in the end to keep their winning run going into next week's Confederations Cup.

Latvia, on a five-match losing run heading into this match, started the better side without asking too many questions of opposition stopper Rui Patricio.

When the Sporting Lisbon keeper was finally called into action 15 minutes in, he barely had to break his stride to keep out a rather audacious attempt from Valerijs Sabala.

Confidence certainly was not lacking as far as the hosts were concerned, though, and Portugal took time to build any sort of momentum in the Latvian capital.

With nearly a quarter of the game played the European champions finally began to show some of their attacking quality, testing Andris Vanins through a Bruno Alves header and then once more from Cristiano Ronaldo's 25-yard drive.

Ronaldo, frustrated by a series of unpunished challenges, grew more and more into the contest and finally made a telling difference on the brink of the interval.

Andre Gomes sent a cross into a deep position, where Jose Fonte was waiting to meet it with his head. The ball hit the post but bounced into the path of Ronaldo, who was there to head home from a yard out to bring up his 601st career goal, six days on from guiding Madrid to Champions League joy in Cardiff.

Portugal dominated the second-half proceedings, however, with Ronaldo finding the target another couple of times in the opening 10 minutes but being thwarted by Vanins.

Latvia did manage an attempt of their own, courtesy of a dipping Olegs Laizans free kick that needed helping over, but from that point on Portugal ran away with things.

A right-sided cross from substitute Ricardo Quaresma deflected into the path of star man Ronaldo to again bundle over the line from close range, before the Madrid superstar laid one on a plate for Silva to tuck home soon after.

Portugal probed for a fourth to improve their goal difference, but they were unable to create any more chances in the remainder and were made to settle for just the three.