Playmaker Vassilis Spanoulis led holders Olympiacos to an 82-74 victory at Unicaja Malaga of Spain, Croatia forward Bojan Bogdanovic steered dark horses Fenerbahce to an 84-68 home win over Budivelnik Kiev and Real Madrid brushed aside Zalgiris Kaunas 95-67.
Elsewhere, former double champions Barcelona romped to an 82-64 rout at injury-hit Partizan Belgrade and fellow Spaniards Laboral Kutxa triumphed 70-65 at Maccabi Tel Aviv, winners of four titles in Europe's premier club competition.
Spanoulis, who inspired Olympiacos to successive titles last season and in 2012, nailed a flurry of three-pointers midway through the final period as the champions wiped out a five-point deficit in Malaga.
He finished with a game-high 21 points and shooting guard Matthew Lojeski added 19 for the Greek side.
"We were not focused in the first half but the second was much better as we were more intense in defence and patient enough to move the ball in offence," Olympiacos coach Georgios Bartzokas told www.euroleague.net.
"It was a great Euroleague game with a fantastic atmosphere and we are very happy to get our sixth win in a row."
The versatile Bogdanovic scored 20 points as Fenerbahce stretched their impressive run with a strong first half against Budivelnik, carving out a 17-point lead.
Fellow Croatian Luka Zoric chipped in with 15 points and Slovenian forward Gasper Vidmar netted 12 to go with 10 rebounds.
It was one-way traffic in Madrid as eight-time winners Real's free-scoring perimeter shooters enjoyed a memorable evening, combining for 12 three-pointers to book their team's ticket in the second group stage of the marathon 24-team competition.
Forward Nikola Mirotic led the way with 17 points, former NBA shooting guard Rudy Fernandez netted 16 and playmaker Sergio Rodriguez amassed 15 in the Palacio de Deportes Arena.
The Top 16 features two pools of eight sides playing each other home and away on a round-robin basis.
The leading four teams from each pool then qualify for the best-of-five quarter-final play-off series.