Sergio Oliveira curled in an 89th-minute free kick to give Porto a valuable 1-0 win at Krasnodar while Celtic held on for a 1-1 draw away to Cluj in Wednesday's Champions League third qualifying round first-leg ties.
LASK Linz pulled off a shock 2-1 win at FC Basel and Olympiakos and Rosenborg also won away, beating Istanbul Basaksehir and Maribor respectively as the five matches produced four away wins and a draw.
Twice former champions Porto, who reached the quarter-finals last season, were indebted to debutant goalkeeper Agustin Marchesin who brilliantly turned over Remy Cabella's close-range shot with 10 minutes to go.
Playing their first competitive match of the season, Porto won a free kick on the edge of the area with one minute left and Oliveira, returning from a six-month loan spell at PAOK, curled his shot over a four-man wall and beyond goalkeeper Matvei Safonov.
"Our final pass let us down a few times but that is understandable at the start of the season," Porto coach Sergio Conceicao said.
"It we had been just a little more assertive, we could have scored more goals. But the most important thing is that the team were compact and decisive."
In Romania, Cluj went ahead after 28 minutes with a goal which started from a Celtic corner. Cluj cleared the ball, broke up field, found Mario Rondon and the Venezuelan thumped his shot past Scott Bain.
But James Forrest replied nine minutes later with a shot which went in off the post.
"It's a great result. Obviously, the away goal's priceless," said Celtic manager Neil Lennon.
"We looked really dangerous. They scored a great goal on the counter attack. Our reaction to the goal was superb."
LASK, who have never played in the Champions League, were seen as rank outsiders against vastly more experienced Basel especially after both coach Oliver Glasner and last season's leading scorer Joao Victor joined Bundesliga side VfL Wolfsburg during the summer.
But captain Gernot Trauner headed the Austrians in front from a corner six minutes after halftime and Joao Klauss scored the second with a deflected shot from the edge of the area before Luca Zuffi pulled one back to give Basel hope for the return.
Giorgos Masouras headed in from Mathieu Valbuena's cross early in the second half for Olympiakos while hosts Istanbul Basaksehir had Irfan Kahveci sent off for a second bookable offence.
Two goals from Alexander Soederlund after halftime set Norwegian champions Rosenborg, who last reached the group stage in 2007-08, on the way to their win over Maribor.
Marcos Tavares pulled one back for the Slovenian champions but Mike Jensen immediately restored Rosenborg's lead.