MARSEILLE, France (AP) — Theo Walcott and Aaron Ramsey scored second-half goals as Arsenal opened its 16th straight Champions League campaign by defeating Marseille 2-1 in Group F on Wednesday.

Walcott capitalized on a miscued clearance from Jeremy Morel to volley into the top corner in the 65th minute. Ramsey doubled the lead with a low strike in the 83rd.

Marseille scored a consolation goal with a penalty from Jordan Ayew in stoppage time.

It was Arsenal's sixth straight victory in all competitions.

"We didn't have a great match but we handled well the key moments," Arsenal manager Arsene Wenger told Canal Plus television. "Marseille had an excellent first half while we were shy. We capitalized on Marseille's drop in form in the second half."

The Gunners showed their attacking flair in the second half despite missing several players through injury.

Napoli beat Borussia Dortmund 2-1 in the other Group F match.

Marseille put the Gunners under pressure in the opening minutes, but Arsenal goalkeeper Wojciech Szczesny saved Pierre-Andre Gignac's close-range backheel flick and a curling shot from Mathieu Valbuena.

Arsenal quickly replied with a header from Walcott, cleared by Nicolas N'Koulou in the third minute, and a half-volley from the England winger that goalkeeper Steve Mandanda stopped in the sixth.

Second in the Premier League, Arsenal struggled to find space as Germany playmaker Mesut Ozil had very little impact in midfield.

A well-organized Marseille team had the better chances before halftime. Ghana winger Andre Ayew headed a cross from Dimitri Payet wide in the 21st before Arsenal centerback Per Mertesacker intercepted a low pass from Payet for Ayew in the 39th.

Gignac beat Mertesacker and Ramsey to the ball in the 40th to connect with a corner from Payet, but sent his header over the bar. On the stroke of halftime, Szczesny came off his line to punch the ball into Gignac's head and was lucky to see the ball bounce his way.

Both teams traded blows in a lively second half that could have gone either way.

"It's a pity because our performance was good," Marseille playmaker Valbuena said. "We had more scoring chances. But it's top-level football. The better team does not always win."

Marseille fullback Rod Fanni took a pass from Alaixys Romao in the 47th but fired wide from close range. The Gunners then threatened in the 53rd when Ozil set up Kieran Gibbs with a backheel pass. However, Mandanda saved the first-time effort from the Arsenal leftback.

The Arsenal defense seemed shaky at times. A cross from Morel eluded the Gunners in the 56th, forcing Szczesny to stop a low half-volley from Payet. Mertesacker then failed to clear a cross from Payet, which looped over Szczesny in the 60th. It took a desperate clearance from Gibbs to clear the ball off the line.

Despite its average defensive display, Arsenal somehow rediscovered its attacking touch. Unmarked at the far post, Jack Wilshere volleyed a cross from Bacary Sagna in the 58th that was saved by Mandanda. Seven minutes later, Gibbs charged down the left flank to make a cross that Morel failed to clear.

Arsenal striker Olivier Giroud in the 72nd and Ozil in the 83rd missed the target, but Ramsey then made a run and beat Mandanda with a low strike from 18 yards that deflected off N'Koulou's leg for his sixth goal this season for the Gunners.

Ramsey was a little too confident inside his area in the second minute of added time. Betrayed by a poor touch, the Wales midfielder tripped Andre Ayew, whose brother Jordan Ayew converted the subsequent penalty.

"They created a lot of problems for us," Giroud told Canal Plus television. "We did not dominate the match but we managed to make the difference on tiny details. That's what the Champions League is about."

Arsenal hosts Napoli on Oct. 1 while Marseille visits Borussia Dortmund.