Vilnius (AFP) - Lithuanian prosecutors said Thursday they have reopened an investigation into allegations that the Baltic nation hosted a secret US interrogation centre for Al-Qaeda suspects a decade ago.

Prosecutors restarted a probe into former secret service chiefs alleged to have hushed up the existence of a US Central Intelligence Agency (CIA) so-called "black site", Rita Stundiene, a spokeswoman for the prosecutors, told AFP.

The investigation was merged with an ongoing separate probe into suspicions that Saudi national Mustafa al-Hawsawi was imprisoned at a secret CIA jail in Lithuania in 2005-2006.

"The prosecutor renewed a previously terminated probe and merged it with the ongoing pre-trial investigation," Stundiene said.

The decision to restart the investigation into possible "abuse of office" was taken in January after the publication of an explosive US Senate report detailing America's torture of "war on terror" detainees, but was only made public Thursday.

Prosecutors initially dropped the investigation four years ago, citing insufficient evidence and the lapse of the statute of limitations.

Human rights activists said the Senate report confirmed suspicions that Guantanamo detainee Hawsawi was imprisoned at a secret CIA jail in Lithuania in 2005-2006, after the country joined the EU and NATO in 2004.

Last December, Lithuanian prosecutors sought more information from US authorities but had yet to receive a reply, Stundiene said.

In 2009, a Lithuanian parliamentary inquiry identified two sites on the territory of the staunch US ally that may have been used as CIA black sites.

But it noted that despite records showing CIA aircraft landed in Lithuania, it was not possible to say if suspects were actually brought in.

In neighbouring Poland, former president Aleksander Kwasniewski last year publicly acknowledged that his country had hosted a secret CIA prison.