Gabriel Martinelli's early goal helped Arsenal maintain their perfect start to the league phase of the Champions League as they overcame Olympiacos.

Having beaten Athletic Club in their first game of the competition thanks to a goal and an assist from the Brazilian forward, he was again crucial for the Gunners.

Striker Viktor Gyokeres powered his way through the Greek side's defence, but when his shot bounced off the post after being saved by Konstantinos Tzolakis, Martinelli was on hand to tap in the rebound.

Substitute Bukayo Saka sealed the success in added time with a shot that squeezed through the legs of Tzolakis.

Anthony Gordon scored two penalties against Union Saint-Gilloise as Newcastle United claimed a convincing first Champions League win of the season.

Newcastle suffered a dramatic defeat at the hands of Arsenal on Sunday, but the clinical visitors looked like a side eager to respond as they secured their first away victory in the competition since 2003.

There was certainly no sign of a hangover at Lotto Park when Nick Woltemade opened the scoring in the 17th minute.

Winger Anthony Elanga whipped a cross into the box and Union could only clear the ball as far as the lurking Sandro Tonali on the edge of the area.

Tonali caught the ball sweetly on the volley and the Italian's effort took a deflection off record signing Woltemade to wrongfoot goalkeeper Kjell Scherpen.

Harvey Barnes added a fourth late on with a fine finish from inside the box to seal the win in Brussels.

Eric Dier's cool last-minute penalty earned a Champions League draw for Monaco against Manchester City, despite Erling Haaland continuing his scintillating start to the season by scoring twice.

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Haaland scored a first-half double to take his tally to 52 goals in just 50 games in the competition as City stretched their unbeaten run to six games.

But the visitors were pegged back in the 90th minute when Dier converted from the spot after being kicked in the head by Nico Gonzalez.

Norway's Haaland had not had a touch of the ball in the first 15 minutes but with his first, he latched on to Josko Gvardiol's dinked pass and lobbed a cool finish over the advancing Philipp Kohn.

Jordan Teze equalised just three minutes later with a thunderbolt strike from outside the area, which arrowed into the top corner and gave Gianluigi Donnarumma no chance.