Arsenal won 2-0 away to Athletic Bilbao as the league phase of this season's Champions League kicked off on Tuesday, with two Kylian Mbappe penalties giving Real Madrid a narrow win over Marseille while Juventus and Borussia Dortmund drew an eight-goal thriller.

Tottenham Hotspur also won on the tournament's opening night which saw outsiders Union Saint-Gilloise and Qarabag claim first ever victories in the Champions League proper.

Arsenal are eager to make a big impression again in Europe's elite club competition, following their defeat by eventual champions Paris Saint-Germain in the semi-finals last season.

They got off to an ideal start in the Basque Country, with Gabriel Martinelli and Leandro Trossard scoring late goals to settle the game.

The Brazilian had only just come on when he ran through to open the scoring in the 72nd minute at San Mames. Arsenal then went on to seal the victory late on as Trossard – another substitute – scored with the aid of a deflection.

"We started to grow throughout the game. In the second half we were more fluent, dominant, and the finishers made the impact for us to win the game," said Arsenal coach Mikel Arteta.

Meanwhile, Real Madrid came from behind to beat Marseille 2-1 at the Santiago Bernabeu, despite playing the closing stages of the game down to 10 men.

Marseille, winners of the inaugural Champions League in 1993, stunned the home crowd by taking the lead through Timothy Weah midway through the first half.

The record 15-time European champions grabbed an equaliser before the interval when Mbappe converted from the spot for the first time after Rodrygo was fouled in the area.

Xabi Alonso's side lost Trent Alexander-Arnold to injury early on and were reduced to 10 men in the second half when his replacement, Dani Carvajal, was sent off following a VAR check for a headbutt on Marseille goalkeeper Geronimo Rulli.

But the home side still snatched all three points thanks to another Mbappe penalty late on after Facundo Medina was harshly penalised for handball.

"For me it's a penalty, but I understand there are people who don't (think so), we're all lost with this rule," Mbappe, who reached 50 goals for the club, told broadcaster Movistar.

Thomas Frank's Spurs, who qualified for the Champions League after winning last season's Europa League, edged Villarreal 1-0 in North London.

The match was decided by a farcical early own goal from Villarreal goalkeeper Luiz Junior, who contrived to let Lucas Bergvall's cross trickle into the net.

The victory maintained Tottenham's impressive form under new boss Frank. "It was a very even game that we just edged," he said. (AFP)