Organisers claimed there were up to 200,000 people at the rally
Tens of thousands of people have marched in Albania's capital to demand reopening ballot boxes from last year's election, amid claims of vote-rigging.
The demonstrators vowed to stay in Tirana's main square until the government gave in to their demands.
Prime Minister Sali Berisha's conservatives narrowly won the general election in June 2009.
Hundreds of policemen guarded the square as the government dismissed the protesters' demands as illegal.
'The final moment'
Socialist leader Edi Rama called on the demonstrators to show "peaceful resistance" during Friday's march, which ended outside the main Albanian government building.
Mr Rama, who is also mayor of Tirana, urged a campaign of disobedience against the government until the demand for a recount was met.
"We must all tell the government that its fate begins and ends with our call: open the ballot boxes or leave," Mr Rama was quoted as saying by the AP news agency.
Mr Berisha's Democrats and allies control 75 of parliament's 140 seats. The Socialists are demanding a recount of several ballots, and have been boycotting parliament for months.
Organisers claimed there were up to 200,000 people at the rally, although there was no official figure. It was the largest street protest against the election result so far.
"This is the final moment," Gramoc Ruci, a Socialist leader, told the crowd.
The BBC's Mark Lowen in Tirana says a sea of protesters were waving Socialist Party flags and that banners accusing the prime minister of fraud and of damaging the economy lined their route.
Albania is facing serious political deadlock, which is damaging its hopes of moving towards European Union membership, he adds.