ANKARA, Turkey — Turkish police have arrested a suspected al-Qaida militant accused of being part of a plot to carry out massive bomb attacks on U.S.-related targets in Germany, German and Turkish authorities said Wednesday.

Attila Selek, 22, a German national, was arrested Tuesday in the central Anatolian city of Konya on charges of membership in a terrorist organization and preparing to carry out bomb attacks.

He was arrested on a German warrant and Berlin has asked for his extradition, said Sonja Heine, a spokeswoman for the German Federal Prosecutor's Office.

She said the accused is suspected of being part of the German terrorist group accused of plotting the attacks.

"The goal of the group was to carry out bombing attacks against American targets or places frequented by American soldiers in Germany, in order to carry out the maximum possible casualties," her statement said.

Selek was allegedly in charge of securing the triggering devices for the bombs, Heine said.

His attorney, Manfred Gnjidic, said Tuesday that he had spoken with his client shortly after his arrest and that he denies the charges.

Selek was transferred to a court in Istanbul for questioning by prosecutors on Wednesday, the state-run Anatolia news agency reported.

A German journalist who was trying to interview Selek at the time of his arrest was also detained by police and was released after questioning, the agency said.

Selek is also accused of scouting a U.S. Army base at Hanau, near Frankfurt, on Dec. 31, along with four other suspects, Heine said. Three were arrested in a sweep in early September. Selek had left for Turkey in February. Details on the suspect at large were not released.

In custody already are two German converts to Islam — Fritz Martin Gelowicz, 28, described as the leader of the German terrorist cell, and Daniel Martin Schneider, 22 — as well as Adem Yilmaz, 29, who was born in Turkey but also was living in Germany.

Prosecutors said they formed a German cell of the radical Islamic Jihad Union, an offshoot of the Islamic Movement of Uzbekistan, a jihadist group with origins in Central Asia.

"Like the other suspects, Attila S. also trained in an IJU camp in Pakistan in 2006," Heine said.

According to the U.S. State Department, the Islamic Jihad Union was responsible for coordinated bombings directed at the U.S. and Israeli embassies in July 2004 in the Uzbek capital, Tashkent. Members have been trained in explosives by al-Qaida instructors and the group has ties to Osama bin Laden and fugitive Taliban leader Mullah Omar.

The German cell had stockpiled 1,600 pounds of highly concentrated hydrogen peroxide at a rented cottage in central Germany in preparation for their plot — enough to build bombs more powerful than those that killed 191 commuters in Madrid in 2004 and 52 in London in 2005, authorities have said.

Officials said they could have mixed the peroxide, purchased from a chemical supplier, with other substances to make explosives equivalent to 1,200 pounds of dynamite.

But German authorities — acting partially on intelligence from the U.S. — had been watching the cell and had covertly replaced all of the hydrogen peroxide with a dilute substitute that could not have been used to produce a bomb.

"The planned attacks were foiled with the arrests of Sept. 4, and at that time, the detonators procured by the accused Attila S. were secured," Heine said.