Tens of thousands of anti-government protesters marched through the Hungarian capital of Budapest, demanding a new election and a new national electoral system in the biggest opposition rally in years.
Prime Minister Viktor Orban was re-elected for a fourth term last week. His right-wing populist Fidesz party won a super-majority in the national assembly, with preliminary results showing that Fidesz and tiny ally the Christian Democratic party won 134 seats in the 199-seat legislature.
Opposition supporters are upset that Hungary's electoral rules have given Mr Orban's party such a large majority in Parliament when it only won around 50% of the vote.
While the left-wing opposition parties won 12 of 18 seats at stake in Budapest districts, Fidesz won 85 of 88 seats outside the capital. The other 93 seats were allocated based on votes for party lists.
Protesters marched from the Opera to Parliament, shouting "New elections!" "We are the majority!"
The size of the crowd, overflowing from the city's Kossuth Square outside Parliament, rivalled the pro-government Peace March held on March 15. Organisers said another anti-government protest would be held next weekend.
"We want new and fair elections," opposition activist Gergely Gulyas told the huge crowd. "This is the responsibility of the government and we're going to remind them of this, peacefully and massively."
Mr Orban, whose campaign focused on the demonisation of migrants, has promised "significant changes" in his next government, which could push for a constitutional amendment against migration.
He claims that opposition parties want to turn Hungary into an "immigrant nation" with the help of the European Union, the United Nations and Hungarian-American billionaire and philanthropist George Soros.
Opposition members deny the claim.