Controversy over secret CIA prisons in Europe rose again Wednesday with the allegations that an upscale Lithuanian horseback riding school was secretly used to interrogate Al-Qaeda suspects.

ABC news, citing unnamed Lithuanian government officials and a former US intelligence official, claimed the riding academy and cafe outside Vilnius was used to interrogate up to eight Al-Qaeda suspects at a time.

The CIA is alleged to have constructed thick concrete pillars inside the facility, which it bought using a front company.

The claim comes after Lithuanian lawmakers earlier this month launched an inquiry to find out if the CIA operated a secret prison for terror suspects and if Lithuanian officials may have been complicit.

In October, Lithuanian President Dalia Grybauskaite ruled out accepting any prisoners from the controversial US Guantanamo detention facility until Lithuania is cleared of allegations it secretly hosted any CIA jails.

Lithuania is the third European country to face accusations of hosting secret CIA prisons during the previous US administration after Poland and Romania.

The so-called black sites are believed to have been used to interrogate suspects using measures which the administration of President Barack Obama has denounced as torture.