The situation has put pressure on Serbia's increasingly autocratic President Aleksandar Vucic, who has refused the protesters' demand to call an early parliamentary election.

The offices of the the ruling Serbian Progressive Party (SNS) have been set on fire during a fifth night of unrest in a row that saw fresh clashes between anti-government protesters and riot police.

Anti-government protesters demolished the offices of the ruling Serbian Progressive Party (SNS) in the northern city of Novi Sad and clashed with police and SNS supporters in the capital Belgrade on Thursday,