Barcelona scored five without reply in Belarus as they ran out comfortable winners against BATE Borisov.
Alyaksandr Valadzko turned a cross into his own net before Pedro nodded in David Villa's lofted pass and Lionel Messi added a third before half-time.
Messi hit a second on 55 minutes and David Villa scored a late fifth.
Barcelona now sit joint-top of Group H with AC Milan on four points, the Italian side beating Czech champions Viktoria Plzen 2-0 at the San Siro.
After a goalless opening 45 minutes, Milan broke the deadlock with a Zlatan Ibrahimovic penalty following a hand-ball, and Antonio Cassano secured three points with a lob over goalkeeper Marek Cech.
Marseille top Group F ahead of Arsenal after a comfortable 3-0 home win over German champions Borussia Dortmund.
Ghanaian Andre Ayew gave his side a first-half lead and Loic Remy scored a composed second before Ayew added a third from the spot. Ayew's younger brother Jordan was sent off in injury time for the French side.
Bayer Leverkusen are Chelsea's nearest challengers in Group E after beating Genk 2-0. German international Sven Bender scored from a tight-angle on the half-hour, and substitute Michael Ballack sealed the win in injury time.
Apoel Nicosia are the unlikely leaders of Group G after they side took a point away at Shakhtar Donetsk. The Cypriot side took the lead in the 61st minute through Macedonian Ivan Trickovski, but Shakhtar levelled through Jadson three minutes later.
Zenit St Petersburg are second in that group following their 3-1 victory over Porto.
James Rodriguez gave the Portugese champions an early lead after hitting home a Hulk cross. Roman Shirokov equalised for the home side on twenty minutes, before Porto had Jorge Fucilesent off in first-half injury time.
The Russian side made their advantage count, with Shirokov netting a second and Danny adding a third after half-time.