MONACO — Barcelona was handed a favourable start to its title defence with Bayer Leverkusen, Roma and BATE Borisov when the Champions League groups were drawn on Thursday.
Lionel Messi scored five of his Champions League record 77 goals against Leverkusen when Barcelona won 7-1 in a last-16 match in 2012.
Real Madrid was placed in a tougher group with Shakhtar Donetsk and Zlatan Ibrahimovic's current and first clubs, Paris Saint-Germain and Malmo.
Europe's four highest-ranked leagues meet in the group of Juventus, Manchester City, Sevilla and Borussia Moenchengladbach.
Manchester United returns after a one-year absence against PSV Eindhoven — the lowest-ranked of the eight top-seeded clubs — plus CSKA Moscow and Wolfsburg.
Chelsea was grouped with coach Jose Mourinho's old club Porto, which he guided to the title in 2004 immediately before starting his first spell at Stamford Bridge. Dynamo Kyiv and Maccabi Tel Aviv complete the group.
Mourinho aims to become the first coach to win Europe's premier club title with three different clubs, after Porto and Inter Milan (2010).
Bayern Munich will again face Arsenal, which it eliminated at the last-16 stage in 2013 and 2014, plus Olympiakos and Dinamo Zagreb.
The trip up to six time zones east to face newcomer Astana in Kazakhstan went to Benfica, Atletico Madrid and Galatasaray.
With UEFA separating Russian and Ukrainian teams in the draw, top-seeded Zenit St. Petersburg was grouped with Valencia, Lyon and Gent. The champion of Belgium is the second club making its debut at the elite level.
The eight groups begin six rounds of play on Sept. 15.
The top two in each group advance to the last-16 knockout round which begins in February.
Graham Dunbar, The Associated Press