TIRANA - Opposition protesters pelted Albania's government building and a mayor's office with petrol bombs late on Thursday, accusing Prime Minister Edi Rama of corruption and demanding his resignation.

Thousands of opposition supporters gathered in front of Rama's office and later at the office of Tirana's mayor who is also from Rama's Socialist Party.

Police did not intervene but did extinguish fires from the petrol bombs which endangered a few officers. There were no immediate reports of injuries.

Protesters also asked for release of opposition leader Sali Berisha who has been held under house arrest and investigated for alleged corruption while serving as prime minister between 2005-2013.

Berisha has denied wrongdoing, accusing Rama of a political vendetta meant to silence opponents. Rama made no comment but has denied this charge repeatedly.

Prosecutors have yet to decide whether to file formal charges against Berisha.

"Albania is the only country in Europe with its opposition leader under political arrest without any facts, evidence or documents," Berisha said via a video link from his house arrest.

"Edi Rama wants an Albania without Albanians, without opposition and without justice."

Berisha has called for supporters to engage in civil disobedience to force the government to hold snap elections.

Rama has held power since 2013 and has won all parliamentary and local elections since then.

  - Reuters