Arsenal have made it two wins from their opening two UEFA champions League fixtures for the 2013/14 campaign.
The Gunners produced an impressive display to beat Napoli 2-0 at the Emirates Stadium to remain top of Group F.
Mesut Ozil scored his first goal for the north London club when he struck home a superbly-timed side-footed effort from just inside the area after being found by Aaron Ramsey in the eighth minute.
The German playmaker then turned provider, cutting back for Olivier Giroud to flash home his sixth of the season to give Arsene Wenger's men a perfect start to the group stage.
In Group E, Chelsea bounced back from their shock Matchday 1 defeat to FC Basel by beating Steaua Bucharest 4-0 in Romania.
Ramires opened the scoring in the 20th minute when he flicked home from close range before an own-goal from Daniel Georgievski gave the Blues a commanding lead on the stroke of half-time.
Ramires made it 3-0 ten minutes into the second half when he fired home from the right side of the box before Frank Lampard rounded off the win with a late low finish from just outside the area.
Barcelona recorded another win but this one was filled with controversy as they got the better of Celtic 1-0 in Group H.
The Scottish giants lost skipper Scott Brown on the hour-mark when he kicked out at Neymar and it proved too be decisive as the Catalan club went ahead in the 76th minute when Alexis Sanchez crossed for Cesc Fabregas to head home to give Tata Martino his second win in Europe's premier club competition.
Elsewhere, Zenit St Petersburg were held to a 0-0 draw by Austria Vienna in Group G as Schalke edged FC Basel 1-0 in Switzerland in Chelsea's Group E.
A brace from Robert Lewandowski allowed Borussia Dortmund to secure a 3-0 home victory over Marseille in Group F, Atletico Madrid came from behind to beat FC Porto 2-1 in Group G and AC Milan required an injury-time penalty from Mario Balotelli to cancel out Ajax's 90th minute goal to force a 1-1 draw in Group H.
Wednesday nights fixtures see Shakhtar Donetsk host Manchester United and Real Sociedad head to Bayer Leverkusen in Group A, Juventus take on Galatasaray in Turin and FC Copenhagen away at Real Madrid in Group B, PSG at home against Benfica and Olympiakos at Anderlecht in Group C as CSKA Moscow meet Viktoria Plzen and reigning champions Bayern Munich head to Manchester City in Group D.
2013/14 UEFA Champions League scores - Matchday 2
Group E
FC Basel (SUI): 0 Schalke 04 (GER): 1 (Julian Draxler 54') St Jakob-Park, Basel, Switzerland - 33,251
Steaua Bucharest (ROM): 0 Chelsea (ENG): 4 (Ramires 20'/55', Daniel Georgievski (og) 44', Frank Lampard 90') Arena Nationala, Bucharest, Romania - 36,713
Group F
Borussia Dortmund (GER): 3 (Robert Lewandowski 19'/(p) 80', Marco Reus 52') Marseille (FRA): 0 Signal Iduna Park, Dortmund, Germany - 65,829
Arsenal (ENG): 2 (Mesut Ozil 8', Olivier Giroud 15') Napoli (ITA): 0 Emirates Stadium, London, England - 59,536
Group G
Zenit St Petersburg (RUS): 0 Austria Vienna (AUT): 0 Petrovsky Stadium, St Petersburg, Russia - 18,785
FC Porto (POR): 1 (Jackson Martinez 16') Atletico Madrid (SPN): 2 (Diego Godin 58', Arda Turan 86') Estadio do Dragao, Porto, Portugal - 33,989
Group H
Ajax (NED): 1 (Stefano Denswil 90') AC Milan (ITA): 1 (Mario Balotelli (p) 90+4') Amsterdam Arena, Amsterdam, Holland - 51,692
Celtic (SCO): 0 (red card: Scott Brown 59') Barcelona (SPN): 1 (Cesc Fabregas 76') Celtic Park, Glasgow, Scotland - 58,128
