By Pawel Sobczak and Gabriela Baczynska
WARSAW (Reuters) - Poland's Prime Minister Donald Tusk on Thursday appealed for more "discretion" around the country's investigation into alleged CIA prisons for al Qaeda suspects on Polish soil, after media revelations about the probe.
Polish media said on Tuesday prosecutors had charged a former head of Poland's intelligence service with helping set up secret CIA detention centers at the height of the U.S. "war on terror" in the early 2000s.
"I did not came up with those charges and, if I were in the prosecutors' shoes, I would not come up with such charges. But maybe I don't have enough information," Tusk told a news conference.
He added those investigating the case "must rise to the highest standards of concern for state interest" and show the "utmost discretion".
Polish officials have repeatedly denied the existence of secret CIA facilities on Polish soil in spite of reports by the European Parliament as well as the Council of Europe saying Poland and Romania hosted such bases.
Human rights activists say the bases served for "extraordinary rendition" of suspects and that prisoners were kept there without necessary court orders and often tortured.
In 2008, Poland launched a classified probe and on Thursday Tusk also said it must clarify the matter to the very end.
"There is no doubt Poland is a democratic country. This is a painful but very clear proof that no politician, even if hand in hand with the biggest superpower in the world, can do something that will never see the light of the day," Tusk said.
"We must act calmly, discreetly and in the spirit of responsibility for the state on this, but we can take no pride in the fact that such cases must be probed in Poland," he said.
Lithuania was the first European country to admit it had hosted CIA prisons following the September11, 2011, al Qaeda attacks on the United States.
Poland's former head of intelligence, Zbigniew Siemiatkowski, and the U.S. embassy in Warsaw declined to comment on the reports by the Gazeta Wyborcza daily and public television's news bulletin Panorama.
Poland has traditionally been one of the staunchest U.S. allies in the EU.
(Writing by Gabriela Baczynska; editing by Andrew Roche)