Two men with suspected links to Islamic extremists were taken into custody by Munich police, and security at the Oktoberfest beer festival has been increased as videos threatening Germany continued to surface on the Internet, officials said Monday.

Two men from Arab countries were arrested Saturday, the same day authorities banned flights over Oktoberfest, said Munich police chief Wilhelm Schmidbauer.

Such bans are usually imposed only during visits by high-ranking state visits. Traffic was also restricted around the Theresienwiese, the 77-acre festival grounds where Oktoberfest is held for 16 days each year. This year's event began Sept. 19.

At least five videos by Islamic terrorist groups such as Al Qaeda and the Taliban have threatened Germany in recent weeks. A video released by the Taliban late Friday included pictures of Oktoberfest and threatened an attack.

In the latest message, a 28-minute audio recording released Monday, Al Qaeda deputy leader Ayman al-Zawahri criticized Germany and Turkey, saying the former is "lying" about the nature of its mission in Afghanistan and accusing Turkey of taking part in a war against another Muslim nation.

Bavarian Interior Minister Joachim Herrmann said Monday that two videos have referred to the festival while leveling threats. But he added, "There is currently no concrete evidence of an attack in Germany."

Schmidbauer said one of the detained men had contact with Bekkay Harrach, who was identified as the speaker in several recent videos threatening Germany for the country's military presence in Afghanistan. The second knew Harrach through a relative.

Schmidbauer would not release their names, but said both men have lived in Munich a long time.

"We are not making accusations of any criminal acts," Schmidbauer said.

Two judges approved a police request to keep the men in "preventative custody" until Oktoberfest ends on Sunday. German authorities have taken similar action in the past, for instance to hold unruly football fans during the World Cup in 2006.

Oktoberfest has been targeted in the past. Saturday's festival opened with a minute of silence to honor the victims of a bomb attack that killed 13 people and injured 200 others on Sept. 26, 1980.