* Poland accused of allowing CIA to run secret jail
* Europe rights court holds first hearing into allegations
* Polish officials say cannot disclose information
* Say domestic investigation must take precedence
By Gilbert Reilhac
STRASBOURG, Dec 3 (Reuters) - Poland declined to tell the European Court of Human Rights on Tuesday whether it had hosted a secret CIA jail on its soil.
Polish officials were questioned for the first time in open court about allegations Warsaw allowed the CIA to hold al Qaeda suspects in a northern Polish forest a decade ago.
Rights campaigners say the case in the Strasbourg-based court could help dismantle the wall of secrecy around "extraordinary rendition", the global programme run by the CIA to detain suspected al Qaeda militants.
But Polish envoys said they could not share information with the court because that could compromise a separate investigation by Polish prosecutors, and because the court could not guarantee the information would be kept confidential.
"The government does not wish to confirm or deny the facts cited by the applicants," Artur Nowak-Far, under-secretary of state in the Polish foreign ministry, told the court.
The judges asked the Polish officials about why their domestic investigation, which has been running for five years, was taking so long. Human rights groups say Warsaw is deliberately dragging its feet.
Janusz Sliwa, one of the prosecutors from the Polish city of Krakow who is working on the case, said it was highly complex. "All that does not allow one to conclude that the investigation in Poland is biased or ineffective," he said, speaking through the court's translator. "It is taking a long time; that does not mean it is slow."
The case against Poland in the European court was brought by lawyers for two men, Saudi-born Abu Zubaydah, and Saudi national Abd al-Rahim al-Nashiri. They are now being held in the U.S. military's Guantanamo Bay jail in Cuba.
They allege they were flown in secret to a CIA-run jail near the Polish village of Stare Kiejkuty, and that Poland broke the law by allowing their detention to take place.
No further hearings in the case are currently scheduled.
Lawyers for the two men told Reuters after the hearing that the weight of the evidence presented to judges was making it harder for the Polish government to keep silent about what happened to their clients.
"A really strong and compelling case has been put here, so in that sense the hearing was very encouraging," said Helen Duffy, representing Abu Zubaydah on behalf of Interrights, a human rights group.
The current case could give clues as to how judges will rule when they hear subsequent cases alleging that Romania and Lithuania also hosted CIA jails.
"This case is of tremendous significance more generally for accountability in Europe, for European complicity in this illegal operation," said Amrit Singh, a lawyer acting for al-Nashiri on behalf of the Open Society Justice Initiative.
Last month, the United Nations Committee Against Torture said it was concerned about the length of time the Polish investigation was taking, and the secrecy around it. It also urged Warsaw to cooperate with the court in Strasbourg.
The United States has acknowledged that, after the Sept. 11 attacks in 2001, it had facilities around the world as part of a programme of "extraordinary rendition" to detain and question suspected al Qaeda militants.
Keeping the detainees on foreign soil meant they were not entitled to the protection afforded under U.S. law.
(Writing by Christian Lowe; Editing by Mark Heinrich)