Portugal, largely amateur or semi-professional and playing in their second World Cup, did their country proud with a display of ambitious rugby, running the ball at every opportunity and forcing the three-time semifinalists into the sort of scrambling defence they expected to need against Fiji, but not against Pool C's outsiders.

Wales were fortunate to reach halftime 14-3 ahead and the expected second-half surge never materialised. With the clock in the red and the bonus point still not secured, however, evergreen No. 8 Faletau peeled off a scrum and smashed his way over.

"We've got to give full credit to Portugal they were brilliant today," Wales co-captain Jac Morgan said. "They really brought that physicality and really tested us a lot of times in that game."

Portugal qualified for the World Cup in dramatic circumstances when Samuel Marques's last-minute penalty earned them a draw against the United States.

In their first appearance since 2007, the scrumhalf had the chance to put the first points on the board on Saturday but stuck his penalty against a post.

Wales claimed the first try after an enterprising Portuguese attack was brought to an abrupt end by a terrible attempted grubber by giant prop Anthony Alves. Wales went the length of the pitch and Louis Rees-Zammit gathered his own kick to score.

That did not deter Portugal, however, and the locals in the crowd roared their appreciation as they ran everything like the wildest French teams of old -- eight of the Portugal team play for French clubs -- but also showed powerful ball carrying.

Wales had centre Johnny Williams yellow-carded for cynically killing the ball as Portugal launched another attack from deep and their attacking mentality finally brought points via a Marques penalty.

Wales had the last word with a pushover try for Dewi Lake to give them a flattering 14-3 lead but it was Portugal's ambitious and hugely entertaining play that was the talk of the stands during the break.

Wales introduced their version of the bomb squad with a new front row and a change at lock 10 minutes into the second half and the fresh legs helped bundle Morgan over for a third try.

If anyone thought Portugal were about to wilt, however, they were badly mistaken. They surged forward with their own replacements bringing new energy and after a superb lineout move Nicolas Martins crashed over for a try welcomed with a huge roar.

Wales needed another try to secure the bonus point and thought they had it after a brilliant steal by Morgan and a magical run by Rees-Zammit sent Gareth Davies over - only for it be ruled out for obstruction.

Portugal had Vincent Pinto bunker yellow-carded, upgraded to red, as his high boot struck Josh Adams in the face and Wales did what they needed to do - just.