German Foreign Minister Frank-Walter Steinmeier was reportedly the target of systematic spying by the US National Security Agency (NSA), according to information released Monday by transparency organization WikiLeaks.

WikiLeaks documented an intercepted conversation or phone call held by Steinmeier on November 29, 2005 shortly after he had completed his first official visit to the United States as foreign minister.

It is unclear with whom Steinmeier was speaking at the time, but the subject of the call was the US Central Intelligence Agency's (CIA) controversial renditions program. It was alleged that the US had used the airspace and airport facilities of cooperating European countries to illegally abduct European citizens and residents in order to interrogate them at secret "black site" prisons.

Steinmeier denied knowledge of the alleged rendition flights in 2005 and according to the intercept, "seemed relieved that he had not received any definitive response from the US secretary of state regarding press reports of CIA flights through Germany to secret prisons in Eastern Europe allegedly used for interrogating terrorism subjects."

Human rights groups have accused the United States of having used the so-called "extraordinary renditions" in order to interrogate suspected terrorists using methods not allowed in the US itself, including torture.

WikiLeaks has revealed what appears to be a years-long effort to spy on the German Foreign Ministry

'Tacit complicity of European governments'

The US has acknowledged that the CIA operated a secret detention program outside its borders, but denied the use of torture. In 2008, Steinmeier again denied Germany had in any way supported the rendition flights at a parliamentary hearing, calling such accusations "utter nonsense."

"Today's publication indicates that the NSA has been used to help the CIA kidnap and torture with impunity. For years the CIA was systematically abducting and torturing people, with the tacit complicity of European governments," WikiLeaks founder Julian Assange said in a statement.

The new documents paint a picture of an apparent years-long NSA effort to spy on the German Foreign Ministry, dating back to before the September 11, 2001 terrorist attacks. The documents reveal a list of 20 phone numbers the NSA targeted for monitoring, two of which were assigned to Steinmeier as well one number potentially assigned to Joschka Fischer, Germany's vice chancellor and foreign minister from 1998 to 2005.

The German Foreign Ministry has not commented on the latest revelations, which come shortly after WikiLeaks revealed the NSA had allegedly spied on top German politicians for decades.

German Green Party parliamentarian Hans-Christian Ströbele demanded an explanation from the government and secret service in light of the latest revelations.

"They must say what they will do now to resolve the spying and avert damage," Ströbele said after Monday's revelations. He also questioned whether Steinmeier in 2006 "actually failed to answer questions regarding US rendition flights over Germany."

bw/cmk (AFP, dpa)