Austrian-born Mohamed Mahmoud, 27, was picked up Tuesday in the southeastern province of Hatay near the Syrian border, a German security official with knowledge of the talks said. The official spoke on condition of anonymity because he was not authorized to discuss the matter. He said Germany has already begun preliminary proceedings to have Mahmoud extradited.
"We are very confident we will get him to Germany," he said.
Nina Bussek, a spokeswoman for the Vienna public prosecutor's office, said Austria was also seeking Mahmoud's extradition on "suspicion of forming a terrorist organization."
Mahmoud was jailed Austria in 2007 for being a leader of the Global Islamic Media Front, which creates and distributes terrorist propaganda videos. Among the accusations, police said he threatened both Austria and Germany with attacks if they did not withdraw military personnel from Afghanistan.
Following his release in 2011, Mahmoud moved to Germany and became an imam with the ultraconservative Salafi movement, which has been growing rapidly in the country by attracting both Muslims and converts. They have been under close observation since 2010, and that was stepped up further last year after they clashed with police in Bonn last year at a rally of a far-right party.
His group, Millatu Ibrahim, was banned last June.
While in Egypt, Mahmoud is also alleged to have produced online German-language videos for the Global Islamic Media Front calling for terrorist attacks in Europe.
It was not immediately clear when he left Egypt or whether he was on his way to Syria when he was arrested in Turkey.
Police officials in Ankara and Hatay province said they did not have any information on the arrest.
Suzan Fraser in Ankara and George Jahn in Vienna contributed to this story.