Unicaja Malaga secured an 89-75 home victory over Fenerbahce Istanbul, Maccabi Tel Aviv triumphed 87-78 at Zalgiris Kaunas and Russian debutants Lokomotiv Krasnodar won 63-62 at Galatasaray.
Partizan, the 1992 champions, bounced back from two straight defeats by beating six-times winners CSKA Moscow 73-72 on Friday thanks to guard Bogdan Bogdanovic who sank 27 points in front of a 20,000 crowd in the Belgrade Arena.
American forward Tarence Kinsey added 15 points and French centre Joffrey Lauvergne chipped in with 11 for the Serbs who had squeezed into the Top 16 that features two pools of eight teams.
"We defied the odds to get this far and tonight we sprang another miracle to beat a team of CSKA's stature," Partizan coach Dusko Vujosevic told a news conference.
"Despite injuries to several key players and being paid late wages due to our severe financial problems, the lads have squeezed the last drop of energy from themselves to reward this wonderful crowd."
Fenerbahce spent heavily in the close-season in a bid to win Turkey's first Euroleague title but a third defeat in a row leaves them with plenty of work to do if they are to reach the playoffs.
Roared on by a full house in southern Spain, Malaga blew Fenerbahce away in the final quarter to improve their record to 2-1 after Slovenian playmaker Zoran Dragic capped an outstanding performance with a game-high 24 points.
The competition's all-time leading scorer Juan Carlos Navarro returned from injury in grand style by scoring 21 points in as many minutes on the court to steer double Euroleague winners Barcelona to an 81-72 victory at Olympiacos.
The 33-year-old playmaker outshone opposite number Vassilis Spanoulis, who inspired Olympiacos to the title in 2013 and 2012, as Barca joined Panathinaikos at the top of their section with a 3-0 record.
Barca centre Joey Dorsey, a former Olympiacos player, said: "It was an emotional night for me and (forward Kostas) Papanikolaou. I was excited to be back here".
Real, chasing a record ninth title, hit top gear in the second half of their 111-87 home rout of top-flight debutants Bayern Munich.
The Spaniards grabbed a staggering 41 points in the third quarter after scraping a slender 48-47 halftime lead, former NBA guard Rudy Fernandez picking up 24 points and five rebounds.
Lithuanian guard Mantas Kalnietis nailed a three-pointer on the buzzer to silence a noisy Istanbul crowd as Lokomotiv downed Galatasaray.
Experienced playmaker Dimitris Diamantidis steered Panathinaikos to a 78-64 home win over Anadolu Efes Istanbul with 17 points and nine assists.