According to the Süddeutsche Zeitung daily, prosecuting attorneys targeted talks between Khaled el-Masri's lawyer, Manfred Gnjidic, and reporters from the German weekly magazine Stern as well as the German public broadcaster ZDF.

Prosecutors were apparently seeking more information about el-Masri's alleged kidnappers and in January this year, requested the Munich District Court to have Gnjidic's phone lines tapped, Stern magazine reported.

Following the eavesdropping, attorneys considered five calls and one text message to be relevant to the investigations.

"Secret service agents don't call up their victims"

Gnjidic has contested the measures as unconstitutional.

Prosecutors have justified their actions by saying el-Masri's kidnappers could have tried to contact him in order to threaten him or offer him a deal.

The Munich-based lawyer Thilo Pfordte, who is representing Gnjidic at the Constitutional Court, said the prosecutors' justification didn't hold water.

"Tapping telephone lines is not going to help in finding el-Masri's kidnappers," he said. "Experience shows that secret service agents do not call up their victims on the telephone."

The Süddeutsche claimed that police and prosecutors used the Munich District Court's decision permitting the tapping for access to the paper's research.

Pfordte said he saw it as more likely that prosecutors were interested in knowing what Gnjidic told journalists than tracking down the kidnapping culprits.

"They knew Gnjidic was talking on the phone with journalists, not with el-Masri's kidnappers," Pfordte said.

German government denies involvement

Two Stern reporters were apparently looking into the identity of "Sam," an unknown man who spoke perfect German and who supposedly interrogated el-Masri in Afghanistan and accompanied him back to Germany.

The German government has denied any involvement in the case.

Hans-Martin Tillack, one of the reporters who was tapped, told the Süddeutsche that the eavesdropping has further consequences.

"I'm shocked that journalists are the subject of the kind of measures that should be used to pursue the culprits," he said.

"It's very dangerous when people start getting the impression that prosecutors can listen in on journalists," Tillack added. "That scares away potential informants."

Prosecutors direct investigation into who allegedly kidnapped el-Masri is moving slowly, according to the Süddeutsche. They have had a list of aliases, provided by Spanish police, of el-Masri's likely kidnappers since the end of 2005. It took German prosecutors months, however, to make further enquires, the paper said.

Tortured in Afghanistan

According to el-Masri, CIA (the US secret service) agents believed he was a terrorist and abducted him in Macedonia at the end of December 2003. He said he was taken to Afghanistan, where he was repeatedly tortured during interrogations before being released in Albania in May 2004.

El-Masri has sued former CIA chief George Tenet and other officials, but the case was dismissed by a US court in May. It ruled that a trial could compromise US security by disclosing secret information, but added that if his story were true, el-Masri was entitled to "a remedy" from the US administration.

El-Masri recently appealed that decision and has demanded an apology from the CIA as well as an explanation for his abduction.

A German parliamentary committee is investigating the affair because of allegations that Berlin had known of el-Masri's plight but failed to act.

Last week, August Hanning, the former head of the German foreign intelligence (BND) said his agency played no part in el-Masri's kidnapping.