European roundup: Cristiano Ronaldo scores as Juventus overcome Sampdoria

In Sunday's other Serie A matches, second-half goals from Dries Mertens and Lorenzo Insigne fired Napoli to a 2-0 win at Parma, Genoa defeated Crotone 4-1 and Sassuolo drew 1-1 with Cagliari.

While Ronaldo was helping Juve off to winning start, his former club Real Madrid had to settle for a goalless draw at Real Sociedad in the opening match of their LaLiga title defence.

Madrid, who this weekend saw Gareth Bale depart for Tottenham, could not find the breakthrough in a clash that could have gone either way at the Anoeta.

Granada and Real Betis, who have both played twice, lead the table on six points after both picked up wins on Sunday, Granada beating Alaves 2-1 and Betis seeing off Real Valladolid 2-0.

Also in Spain, veteran striker Alvaro Negredo scored the opener as Cadiz downed Huesca 2-1 in the battle of the promoted sides.

In the opening round in Germany, Wolfsburg and Bayer Leverkusen shared a goalless draw as RB Leipzig kicked off their campaign with a 3-1 win over Mainz.

An Emil Forsberg penalty and a Yussuf Poulsen effort put last season's Champions League semi-finalists in charge and although Jean-Philippe Mateta pulled a goal back, Amadou Haidara wrapped up the points for the hosts.

Ligue 1 leaders St Etienne saw their 100 per cent start to the season come to an end after losing a two-goal lead to draw 2-2 at Nantes.

Adil Aouchiche and Yvann Macon put the visitors in the driving seat but Nantes hit back through Moses Simon and Renaud Emond, whose 86th-minute equaliser denied St Etienne a fourth successive win.

Defending champions Paris St Germain secured back-to-back victories – having started the season with successive defeats – by brushing aside Nice 3-0 away from home.

Kylian Mbappe's opened the scoring with a penalty and Angel Di Maria struck at the end of the first half before Marquinhos wrapped things up with a near-post header midway through the second period.

Montpellier recorded a third consecutive win after defeating Angers 4-1, Andy Delort netting twice, while Marseille salvaged a 1-1 draw at home to Lille and Brest defeated Lorient 3-2.

At the other end of the table, Metz and Strasbourg picked up their first points of the campaign after beating fellow strugglers Reims and Dijon respectively.

In Holland, Ajax joined the three other teams boasting a maximum six points after beating 10-man RKC Waalwijk 3-0.

Dusan Tadic opened the scoring after 10 minutes and Zakaria Labyad made it 2-0 in the 35th minute.

RKC lost Luuk Wouters to a red card midway through the second half and Lisandro Martinez added a third goal for Ajax soon after.

Feyenoord and FC Twente dropped their first points of the campaign as they drew 1-1 at De Kuip.

Evangelos Pavlidis started and finished the scoring as Willem II thrashed Heracles 4-0 – all four goals coming in the second half – while FC Groningen won 1-0 at ADO Den Haag.