Second-half goals from Toni Kroos and Thomas Mueller gave holder Bayern Munich a 2-0 victory over 10-man Arsenal and a firm grip on their last 16 Champions League tie on Wednesday.

Kroos scored in the 54th minute with a stunning strike, curling the ball past Arsenal goalkeeper Lukasz Fabianski, who came on after Wojciech Szczesny was sent off for fouling Arjen Robben.

An unmarked Mueller scored with a powerful header from close range in the 88th.

Both teams missed penalties in the first half with Arsenal playmaker Mesut Ozil shooting straight at Manuel Neuer and Bayern midfielder David Alaba clipping a post. Szczesny was sent off in the 37th minute for following through on Robben.

Arsenal manager Arsene Wenger was clearly frustrated by the sending off, saying it was a great game until halftime.

"It killed the game," Wenger said. "The game until then was top quality.

"The second half was boring. It was one-way traffic."

He said Szczesny went for the ball and suggested the decision would have been different had it been a Premier League match.

Bayern coach Pep Guardiola disagreed with Wenger, saying he thought it was a penalty and a sending off. Guardiola acknowledged, however, that Arsenal were the better team in the first 15 minutes and that the sending off worked to his side's favour.

"The game changed completely," Guardiola said. "They had nine players in the box and we had to wait patiently."

With the odds clearly stacked against the London side, Arsenal can only hope it repeats last year's 2-0 win at Bayern in the second leg on March 11. In the night's other match, Atletico Madrid forward Diego Costa scored a late winner to beat AC Milan 1-0 at San Siro.

At Emirates Stadium, the match was breathless until the sending off, with both sides attacking and trying to gain an advantage. Kroos nearly opened the scoring for Bayern in the third minute when he forced Szczesny to make a flying save with his fingertips.

Arsenal wasn't unnerved and starting to dictate play with chances for surprise starter Yaya Sanogo and Santi Cazorla. Bayern's defence started to panic and Ozil won a penalty in the eighth minute when centre back Jerome Boateng clattered into him as the German swiveled past.

However, the playmaker failed to convert the spot-kick and Neuer palmed the ball to safety. It was Ozil's second penalty miss in the Champions League this season, after misfiring against Marseille in the group stage.

Alex Oxlade-Chamberlain created problems down the right for Bayern, but the five-time European champion settled down and started to stretch Arsenal's defence as the first half wore on.

Robben won a penalty in the 37th, when he jumped to control a ball, which bounced off his knee and appeared to be going out of play. But Szczesny was sent off when he clattered Robben's shin on the follow-through.

Fabianski came on and Alaba's spot kick clipped the outside of the left post. Bayern dominated the second half and despite resolute defending from Arsenal, the home side finally caved in.

The first goal came out of nowhere with a simple exchange of passes on the right, but Kroos was given too much space and he unleashed a shot from about 20 yards. A tired Arsenal back line switched off late in the second half with Philip Lahm finding Mueller whose header bounced into the ground past Fabianski.

Kroos nearly made it 3-0 with a low shot that struck a post in stoppage time.

Bayern won the treble last year under Jupp Heynckes and his successor, Guardiola, is on course to replicate the team's domination of European football.

The Germans are unbeaten in the Bundesliga this season, winning 19 of 21 league matches, and are 16 points clear at the top. Guardiola was without injured attacking midfielders Franck Ribery and Xherdan Shaqiri.

The only surprise in team selection was Wenger's decision to start Sanogo over striker Olivier Giroud, who recently was accused of having an affair with a model at a hotel before Arsenal's 5-1 loss to Liverpool. Wenger insisted he wasn't punishing Giroud, just resting him.

"I decided to give him a breather for one, two games," he said.

Atletico 1, AC Milan 0

Atletico Madrid struggled throughout, but managed to win 1-0 at AC Milan, thanks to a late Diego Costa header in the first leg of their last-16 Champions League tie on Wednesday.

Diego Costa headed in Gabi's corner seven minutes from time to secure victory ahead of the return match in Madrid on March 11.

"We know that at Madrid it will be another game, which will also be important and very difficult," Milan coach Clarence Seedorf said. "Atletico don't change much, whether they're playing at home or away from home.

"We have time to prepare the return leg and we'll have more players back. I'm proud of what we did tonight ... I saw a lot of positive things on the pitch."

Milan had dominated the match with its best performance of the season, hitting the woodwork three times in an entertaining first half hour.

"We are a normal team, a very humble one which tries to do as well as we can," Atletico coach Diego Simeone said. "We started better

"But then, Milan caused us problems. We didn't have many chances.

"But as you know, in football, what matters is scoring goals. Fortunately, we scored a goal."

Spain's joint league leader was the overwhelming favourite, but Milan was the superior side and had the better chances in Seedorf's first Champions League match as a manager. The Dutchman is the only player to have won the competition with three different clubs.

There was more bad news on the night for Milan as star striker Mario Balotelli went off clutching his shoulder 12 minutes from time. The Italy forward will have tests on Thursday.

Milan was boosted by key playmaker Kaka recovering from injury in time and the Brazilian was given the captain's armband. Kaka overcame a bout of 'flu to play in Friday's 1-0 victory over Bologna, but had to be replaced 10 minutes from time after injuring his right ankle.

Stephan El Shaarawy, Valter Birsa, Robinho, Bryan Cristante and Cristian Zapata were all out with injury while Sulley Muntari and captain Riccardo Montolivo were both suspended. New signing Keisuke Honda is cup tied.

Milan was the underdog after a miserable season which saw coach Massimiliano Allegri sacked at the beginning of the year. The side is ninth in the Serie A table and had been eliminated in each of its past four knockout ties against Spanish opposition.

It appeared as if Milan's fears were to be realized as the players struggled to get out of their own half in the opening 10 minutes.

However, Milan was containing Atletico and slowly began to get into the game.

Balotelli had the first real chance of the match with a 30-meter free-kick from roughly the same position that he scored a stunning goal from on Friday. But the Italy forward fired well wide of the left post.

Milan went even closer four minutes later with a wickedly swerving shot from Kaka from the bottom corner of the penalty area which crashed off the crossbar.

Atletico goalkeeper Thibaut Courtois — who is on loan from Chelsea — pulled off a stunning save shortly afterwards, fingertipping Andrea Poli's header off the base of his right post after a great cross from Adel Taarabt.

Tension was beginning to escalate at San Siro and a touchline brawl threatened to erupt following a poor Emiliano Insua tackle on Mattia De Scglio. The Milan defender had to be replaced by Ignazio Abate.

Milan again went close on the half hour when Balotelli backeeled the ball to Kaka, whose effort scraped the top of the crossbar.

Milan continued to dominate after the break and Kaka again went close with a drive narrowly past the left upright, while Michael Essien headed a corner wide.

All Milan's good work was to come to nothing, though, as Diego Costa headed powerfully home at the far post for his fifth goal in four Champions League matches.

Milan almost snatched a draw but Adil Rami's free kick whistled wide of the left post.