Police detain Bulgaria's former PM Borissov in blackmail investigation

The decade-long rule of Borissov, 62, ended last spring when he lost an election that showed popular anger over high-level corruption in the European Union's poorest member state. He remains leader of centre-right GERB, the largest opposition party.

A new centrist coalition government took office in December, pledging zero tolerance on graft in Bulgaria, which is ranked as the EU's most corrupt member state by Transparency International.

Former finance minister Vladislav Goranov and GERB's media adviser Sevdalina Arnaudova were also detained late on Thursday for 24 hours, prosecutors said in a statement.

The interior ministry said on Thursday the arrests were part of an operation linked to some 120 investigations by the European Public Prosecutor's Office (EPPO), which investigates large-scale fraud with EU funds, in Bulgaria.

However, prosecutors said that the fact that police had informed them of the blackmail allegations and the detentions suggested the case did not come under the mandate of EPPO.

Sofia City Prosecutors will have to decide later on Friday whether to extend Borissov's detention to 72 hours or release him, after examining the details of the investigation, they said.

The GERB party has decried the arrests, labelling them a political "repression" and called for early elections. Hundreds of GERB activists protested for hours in front of the government building.

Borissov has repeatedly denied any wrongdoing to different allegations of graft-prone activities in the past decade.

Prime Minister Kiril Petkov welcomed the probe and said police have shown that no one was above the law.

"Only without fear from the untouchables can Bulgaria truly change," Petkov said. "Untouchables" is an ironic term used by Bulgarians to refer to high-ranking officials who act as though they were above the law.