FRANKFURT, Germany -- Defender David Alaba scored two goals as Bayern Munich eased to a 4-0 victory over Schalke on Saturday to open a 15-point lead in the Bundesliga.
Bayern, seeking to win its first title after two seasons without a trophy, was helped by the mishaps of its two closest challengers.
"It's a comfortable lead, but we have to keep playing like this and not be blinded by praise," coach Jupp Heynckes said.
Son Heung-min and Artjoms Rudnevs scored two goals each for Hamburger SV to stun defending champion Borussia Dortmund 4-1 in a match that both teams finished with 10 men.
Dortmund's Robert Lewandowski and Hamburg's Jeffrey Bruma were sent off in separate incidents.
Hosts Dortmund stayed second because Bayer Leverkusen was held to a 3-3 draw at Borussia Moenchengladbach. Leverkusen trailed twice before letting a 3-2 lead slip away. Dortmund is one point ahead of Leverkusen but now 15 behind Bayern.
Stuttgart fell to its fifth straight loss in a 4-1 defeat at home to Werder Bremen, Wolfsburg won 1-0 at last-place Greuther Fuerth, Hannover edged Hoffenheim 1-0 and Eintracht Frankfurt blew a chance to move up to third when it was held to a 0-0 draw at home by Nuremberg.
Franck Ribery, who had hit the post early in the match, earned a penalty for Bayern when he was brought down by Marco Hoeger and Alaba converted it in the 19th for the hosts' first goal.
Bastian Schweinsteiger drove in a perfectly executed free kick in the 32nd, curling the ball over the wall and off the post into the net to double Bayern's lead.
Alaba got his second in the 57th off a feed from Mario Gomez. Gomez, who returned to the starting lineup, completed the win in the 64th after a pass from Arjen Robben, who was also in the starting 11 for the first time in several matches.
"We have a deep squad and a good spirit in the team," Heynckes said.
Schalke was missing several injured regulars and now has only one win from its last eight matches.
Lewandowski, who has been repeatedly linked by some German media with a summer move to Bayern, scored his 14th goal of the season in the 17th minute but was sent off in the 31st after taking a wild volley swing and hitting Hamburg's Per Ciljan Skjelbred.
After the foul, Hamburg's Rafael van der Vaart got into a push-and-shove altercation with Sebastian Kehl but escaped with a yellow card. He drew the ire of Dortmund fans, however, and was hit on the head with an object thrown from the stands when he was taking a corner. Van der Vaart was unhurt.
Bruma was sent off in the 59th for a professional foul on Marco Reus but Dortmund was unable to mount a comeback and fell to its third home loss of the season. Hamburg also won the home leg 3-2 to snap Dortmund's 31-match unbeaten run over two seasons.
"We took a long time to get into the match," said Dortmund's coach Juergen Klopp, who reshuffled his lineup ahead of the Champions League match at Shakhtar Donetsk on Wednesday.
"Then we scored but conceded in the very next minute. They went ahead, our guy got the red card ... we still had some good chances but everything went against us today," Klopp said.
Lewandowski exploited an error from Heiko Westermann to score through goalkeeper Rene Adler's legs, but Hamburg struck right back one minute later when Dennis Aogo sent a perfect low cross for Rudnevs to knock into the net from close range.
Son got his first in the 26h with a spectacular shot inside the far post from the right side of the penalty area.
After the break, Rudnevs headed in a cross from Van der Vaart and Son completed the victory by easily stroking in a pinpoint pass from Marcell Jansen at the far post.
Patrick Herrmann's header from close range in the 86th allowed Moenchengladbach to clinch a point against Leverkusen, which remained unbeaten in Moenchengladbach since 1989.
The host team led twice -- scoring twice against the run of play -- but Leverkusen fought back to take a 3-2 lead on Andre Schuerrle's goal in the 65th, only to see Herrmann level the score.
Martin Stranz put the hosts ahead with a header in the 44th, before Sydney Sam tied the match. Luuk de Jong's diving header restored 'Gladbach's lead, but Stefan Kiessling made it 2-2 with his 100th Bundesliga goal. Kiessling now also has 14 goals this season.
Stuttgart's crisis deepened as it fell to 14th place.
Mehmet Ekici scored two goals and Aaron Hunt and Kevin de Bruyne added the others. Ibrahima Traore briefly revived Stuttgart's hopes with his equalizer.
In Frankfurt, police clashed with Nuremberg fans outside the stadium as security was stepped up for the match after reports that Nuremberg fans would try to sneak in flares. Hundreds of Nuremberg fans were late entering the stadium because of stricter controls.
Police banned the visiting fans from taking in flags and banners and used sticks to control the crowd, which responded with pepper spray. Police said 10 officers were injured, along with an unknown number of fans.
Hoffenheim's new Brazilian goalkeeper Heurelho Gomes got his timing wrong in the 8th minute as Mame Diouf headed in the winner for Hannover.
Bas Dost scored in the 23rd for Wolfsburg to beat Greuther Fuerth.