(CNN) -- Rivals Manchester City and Manchester United prospered in the unfamiliar territory of the Europa League as both recorded away victories in the first leg of their last-32 ties.
English Premier League leaders Manchester City had to rely on an Alvaro Pereira own goal and a late strike from Argentina striker Sergio Aguero to seal a 2-1 win at Portuguese champions Porto.
United, the current English champions, won 2-0 over Ajax in the Netherlands thanks to goals from England winger Ashley Young and Mexico striker Javier Hernandez.
Both sides were making their first appearance in Europe's second tier competition after being knocked out of the European Champions League before the turn of the year.
United, two points behind City in the EPL, are now firmly in the driving seat ahead of next week's second leg at Old Trafford.
Manager Alex Ferguson, who has led his side to two Champions League titles during his 25-year tenure at the club, told reporters: "I'm delighted with the scoreline.
"It was a very ordinary performance by us. We didn't reach any great heights in the game but we did improve in the second half and we deserved to win.
"It gives us a good opportunity. We're not taking anything for granted but at home, at Old Trafford -- we've now got a good opportunity to get through."
Young, playing only his second game after a six-week injury layoff, grabbed the first when he collected Nani's cross and cut inside his man to drill the ball into the net.
And late in the game, a United counter attack saw Hernandez swap passes with England striker Wayne Rooney, before finishing past Ajax goalkeeper Kenneth Vermeer.
In Portugal, City went behind in the 26th minute when Varela tapped home Hulk's cross. But after the break Pereira turned the ball into his own net under pressure from Italian striker Mario Balotelli, before Aguero converted Yaya Toure's cross late on.
Elsewhere, two goals from former Porto striker Falcao handed Spanish club Atletico Madrid a 3-1 win at Lazio, who are third in Italy's Serie A.
Atletico's compatriots Athletic Bilbao didn't fare so well on the road however, losing 2-1 to Lokomotiv Moscow in the Russian capital -- goals from Dennis Glushakov and Felipe Caicedo canceling out Iker Munain's opener.
A late goal from Filipe Andre Santos rescued a 2-2 draw for Portuguese outfit Sporting Lisbon against Legia Warsaw in Poland. Jakub Wawrzyniak and Janusz Gol scored for Legia either side of Daniel Carrico's strike.
Adam Maher's goal gave Dutch side AZ Alkmaar a slender advantage to take to Belgium next week after defeating Anderlecht 1-0.
Ukrainian club FC Metalist Kharkiv all but sealed a place in the last 16 with a 4-0 win at SV Salzburg in Austria, Jonathan Cristaldo grabbing two goals.
A goal from Dutch striker Klaas-Jan Huntelaar secured a 1-1 draw for German side Schalke against Viktoria Plzen in the Czech Republic.
A stunning strike from Turkey international Mehmet Topal handed Spanish club Valencia a 1-0 win at English Premier League side Stoke.
Jan Schlaudraff's penalty completed a comeback victory for Germany's Hannover 96 over Club Brugge. Maxime Lestienne handed the Belgian side the lead before Artur Sobiech equalised.
Ola John's 52nd-minute goal gave Dutch club FC Twente victory over Steaua Bucuresti in the Romanian capital, while Italy's Udinese drew 0-0 with PAOK Salonika of Greece.
Polish side Wisla Krakow drew 1-1 with Standard Liege despite playing for 65 minutes with 10 men. Gohi Bi Zorro Cyriac put the Belgian visitors ahead before Tsvetan Genkov's 87th-minute leveler.