Albania’s main opposition leader on Tuesday urged Prime Minister Edi Rama to call a snap election over allegations of corruption and vote fraud, as anti-government protesters rallied outside parliament, Reuters reported.

They burnt portraits of Rama and threw firecrackers at the building, but the demonstration – the fourth against his administration since mid-February and timed to coincide with parliamentary sessions – was calmer than in previous weeks.

The opposition Democratic Party and its allies gave up their parliamentary seats 12 days ago, saying investigations by prosecutors into allegations of vote fraud vindicated claims that Rama’s Socialists fixed the 2017 national election.

Rama, who has rejected the allegations, told lawmakers on Tuesday that democracy was not up for “negotiation” and urged the opposition to test its strength at the ballot box in local elections in June.

Democratic Party head Lulzim Basha called parliament a hotbed of “crime and corruption”. He told Tuesday’s crowd, which Reuters estimated as numbering more than 5,000, that only “free and fair elections” would pave the way for Albania’s entry to the European Union.

The Balkan NATO-member country aims to start accession talks with the EU this year, but the febrile political climate could delay that process.

The European Union and its member states last month called on all sides to “do their utmost to avoid violence and further unrest”.

The next protest is scheduled for 11 days’ time.