LONDON: Porto punished two goalkeeping blunders to beat Arsenal 2-1 and Bayern Munich's late winning goal in a 2-1 victory over Fiorentina was clearly offside on a dramatic night in the Champions League.

Backup Arsenal goalkeeper Lukasz Fabianski fumbled a cross from Silvestre Varela into his own net to concede the opening goal and then handled a backpass by teammate Sol Campbell prior to Porto's second goal. Although Campbell's header had made it 1-1 for his first Champions League goal since the 2006 final, the second strike by Falcao — from a quickly taken free kick after Fabianski's error — gave two-time European champion Porto a first-leg victory to take to London.

Arsenal manager Arsene Wenger criticised referee Martin Hansson, the Swedish official who didn't see Thierry Henry's deliberate handball against Ireland in a World Cup playoff in November which helped France reach this summer's finals in South Africa. Wenger said Hansson was wrong to rule Campbell had passed the ball back to his keeper and, having given the free kick, should have allowed his defenders time to prepare for it.

Bayern made it 13 victories in a row in all competitions by beating Fiorentina in Munich. Arjen Robben fired the German side into a halftime lead with a penalty in the third minute of first-half stoppage time, the Dutch winger scoring for the sixth game in a row.

Per Kroldrup, who had given away the penalty for a foul on Franck Ribery, replied for Fiorentina early in the second half but Miroslav Klose headed the winner in the 89th minute from an offside position.

Fiorentina midfielder Massimo Gobbi was sent off in the 73rd minute by Norwegian referee Tom Henning Ovebro for a bodycheck on Robben.

Manchester United came from behind to win 3-2 at AC Milan and Lyon beat nine-time European champion Real Madrid 1-0 in Tuesday's first-leg games. The remaining four first-leg matches are scheduled for next week.