Champions League Images: Porto sink Arsenal

A controversial Radamel Falcao effort gave Porto a 2-1 win over Arsenal in their Champions League last-16 first leg on Wednesday. But the English side will take heart from Sol Campbell's away goal on his return to the tournament after four years.

Porto had started strongly and their attacking intent paid off in the 11th minute when Fabianski bungled Silvestre Varela's cross into his own net.

Porto could have taken the lead again on 28 minutes when midfielder Micael's drive was blocked by Fabianski.

Falcao's controversial 51st-minute goal shook the Arsenal side and they were unable to create clear chances until the end of the game, with Theo Walcott's introduction on 68 minutes adding little bite.

The Portuguese champions gave Arsenal too much room right after their opening goal and the English side took advantage to equalise.

Campbell, playing in the Champions League for the first time since scoring for Arsenal the 2006 final, was left unmarked at a corner and headed a goal in the 18th minute.

Arsenal's back four, who looked tentative at the start, improved after the half-hour and, with Porto were struggling to defend in the air, a Nicklas Bendtner header forced Helton to tip over the bar.

Porto searched briefly for a third goal, with Hulk and Raul Meireles forcing Fabianski to tight saves, but tired in the last 15 minutes and did not pose much of a threat either as the game petered out.

Arsenal coach Arsene Wenger was left fuming at referee Martin Hansson for the 51st-minute goal after his side were caught napping when Ruben Micael quickly took an indirect free-kick in the box to give Falcao the easiest of tap ins.

The Swedish referee, who was at the centre of the storm around Thierry Henry's handball in France's World Cup playoff against Ireland last year, penalised a Campbell back pass to keeper Lukasz Fabianski and then allowed the free-kick to be taken instantly.

Substitute Miroslav Klose headed an 89th minute goal to give Bayern Munich a 2-1 win over Fiorentina in their Champions League last 16 first leg tie on Wednesday, their 13th straight victory in all competitions.

Bayern started nervously, committing several blunders in defence. At one point Martin Demichelis gave the ball straight to Marco Marchionni as he tried to start a move from defence while another mix-up led to a furious argument between goalkeeper Joerg Butt and Daniel van Buyten.

Bayern went ahead with an Arjen Robben penalty in first-half stoppage time after a foul on Franck Ribery.

Per Kroldrup levelled for Fiorentina five minutes after the re-start, turning in the ball from close range after a corner.

Fiorentina had Massimo Gobbi sent off for an apparent elbow in Robben's face in the 73rd minute.

The Italians, already upset at the red card, were furious about the winning goal, claiming that Klose was offside when the ball was headed to him by Ivica Olic after Fiorentina goalkeeper Sebastien Frey had parried a long-range shot.

Norwegian referee Tommy Henning Ovrebo, at the centre of controversy for his handling of the Chelsea-Barcelona semi-final last season, confirmed the goal amid furious protests from the Italian side.

Despite benefiting from the goal in the 2-1 win, Bayern coach Louis van Gaal was quick to add his name to the list of those who want some form of aid for officials at top games.

"It was clearly offside," said the Dutchman, refreshingly honest in a situation where many of his colleagues might have simply said they did not see the incident.

"I've been banging on about this for 10 years. There is so much interest in our world of football that we can not any more go without technological assistance.

"This time, we were lucky, but against Girondins Bordeaux in the group stage, we were on the wrong end."

Fiorentina coach Cesare Prandelli did not want to go into the merits of possible solutions.

"It was a clamorous mistake," he said.