Portugal marked their return to the World Rugby U20 Trophy after a one-year absence with a tense 20-18 victory over hosts Uruguay on a competitive but extremely wet opening day in Montevideo.

Heavy rain fell throughout as the European champions, competing in their third U20 Trophy, recorded only their second win in the pool stages after out-scoring the more fancied Los Teritos three tries to two.

Promotion-seeking Japan also beat South American opposition in the form of Chile but did not have it all their own way, edging another tight contest 28-22, while African U19 champions Namibia kicked off proceedings with a 31-16 win over Canada. Fiji, placed third in the 2016 edition of the Trophy, saw off Hong Kong 26-7 in the final match of the day at the Estadio Charrua.

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NAMIBIA 31-16 CANADA

Namibia raced into a 12-0 lead inside the first quarter and never looked back as they got their campaign off to the perfect start. With their pack in the ascendency, the African champions forced the agenda, scoring five tries to Canada’s two to also claim a bonus point.

Lachlan Currie and Jake Thiel touched down for the North American representatives, while Will Kelly slotted two penalties. However, the Canadians were undone by the try-scoring of Namibia’s Obert Nortje, PW Steenkamp, Prince Gaoseb, Brandon Groenewald and Patrick Schickerling.

Cliven Loubser, like Nortje already capped at test level by Namibia in 2017, added three conversions.

"It was a tough day today," said Canada coach Jeff Williams. "We didn't play to the conditions, we made too many technical errors and with two yellow cards (conceded at the start and end of the second half), we were unable to generate any momentum. Credit to Namibia because they stuck to their game plan and used the maul effectively."

PORTUGAL 20-18 URUGUAY

Portugal overcame the loss of two players to the sin-bin midway through the second half to pull off the shock of the opening day.

The European champions adapted to the wet surface the quicker of the two, building up a 17-3 half-time lead thanks to tries from their captain Antonio Vidinha and Jose Luis Cabral and seven points from the boot Jorge Abecasis.

Alejo Piazza replied with a penalty for Uruguay and added a second at the start of the second half, before Los Teritos’ scrum strength earned them a penalty try and cost Portugal their first yellow card.

Portugal defied the loss of a man to increase their lead to 20-13 following Abecasis’ third penalty but the momentum shifted back to Uruguay when they saw yellow for the second time.

Despite a frantic finale, Los Teritos could only manage an unconverted try from Yamandú Arburúas to leave them two points in arrears.

JAPAN 28-22 CHILE 

Missed kicks cost Chile dear as Japan overcame a shaky start to begin their bid to gain promotion back to the World Rugby U20 Championship on a winning note.

Crucially for Chile, seven points went begging from the tee in the first half as Tomas Salas was unable to convert tries from Domingo Saavedra and Rodrigo Gajardo as well as putting a penalty wide.

Chile led 10-3 at the end of the first quarter but they trailed by a point at half-time after a second penalty from Tomoki Kishioka was followed by a try from Hinata Takei.

Another rolling maul led to Takei touching down for his second in the 52nd minute before Chile quickly responded with a try from Vicente Huete. This time Salas was able to add the extras and bring Chile to within a point of the Japanese.

Japan’s dominant pack looked to have sealed the win with a penalty try but a late score for Chile number eight Clemente Saavedra made for a grandstand finish. The last say, however, again went to Japan as Kishioka sent over his third penalty of the day in stoppage time.

FIJI 26-7 HONG KONG

It took a two-try salvo within the final 10 minutes for Fiji to finally douse Hong Kong’s spirited resistance.

An even first-half saw Fiji leading 7-0 at the break thanks to Temo Sukayawa Mayanavanua’s eighth-minute score and Jamie Kotz’s conversion.

But Hong Kong were back on level terms within eight minutes of the restart when captain and scrum-half scrum half Mark Coebergh dived over and Matt Worley added the conversion.

However, Fiji regained the lead through Apisalome Bogidrau, who went on to score a second late in the match, shortly after Lekima Nasamila had touched down for their third try.

The U20 Trophy continues on Saturday with Portugal and Hong Kong kicking off proceedings at the Estadio Charrua in Montevideo, followed by Namibia and Chile. Japan and Canada are third up before the second round comes to a close with Fiji against Uruguay.