State prosecutors said the suspects had been identified on the basis of a list compiled with the help of Spanish authorities.

The list purports to detail those who were on board the aeroplane Masri said took him to Afghanistan.

Additional information about the identities of the suspects was provided by prosecutors in Milan and Dick Marty, a Council of Europe investigator , prosecutors added.

"These findings ... have now provided the grounds for the strong suspicion that 13 identifiable persons participated in the abduction of al-Masri," prosecutors said.

Al-Masri's case has fuelled debate in Europe about secret transfers of alleged terrorism suspects by US intelligence agencies.

Further investigations would concentrate on establishing the real identities of the suspects, prosecutors added.

German NDR state television said the 13 suspects were CIA employees, according to its own research. It said the majority of them were in North Carolina in the United States.

US 'unco-operative'

NDR noted that the German arrest warrants were not valid in the United States and that US authorities had refused to co-operate with the investigation.

If the suspects were to travel to the European Union, however, they could be arrested.

Beyond the criminal investigation, the German parliament has launched a probe into al-Masri's case that has heard witnesses including Frank-Walter Steinmeier, the foreign minister, and his predecessor Joschka Fischer.

Al-Masri is also pursuing a $75,000 compensation claim against the CIA in US courts.

He is one of the most high-profile cases of the "extraordinary renditions" undertaken by the CIA as part the US' "anti-terror" measures.