Hungarian prime minister Viktor Orban said his "decisive" re-election victory and the super majority in parliament his right-wing populist party appeared to have won on Sunday were "an opportunity to defend Hungary."
Critics said they feared Mr Orban will use his third consecutive term and the Fidesz party's two-thirds control of Hungary's national legislature to intensify his attacks on migration and to strengthen his command of the country's centralised power structure.
Hungary's remaining independent media, the courts that have made numerous rulings the government did not like and a university founded by Hungarian-American billionaire George Soros, also are among Mr Orban's likely targets.
"We created the opportunity for ourselves to defend Hungary," Mr Orban told a rapturous crowd after his landslide win became indisputable. "A great battle is behind us. We have achieved a decisive victory."
With 98.5% of the votes counted, Fidesz and its small ally, the Christian Democrat party, together had secured 133 of the 199 seats in parliament, the minimum needed for a two-thirds majority.
The right-wing nationalist Jobbik party placed second with 26 seats, while a Socialist-led, left-wing coalition came in third with 20 seats.
"As the results stand, Fidesz performed much better than expected," Tamas Boros, co-director of the Policy Solutions think tank, said. "There were no small victories for the opposition."
Mr Orban won his fourth term overall on a platform that openly demonises migrants to Europe. He first governed in 1998-2002 before returning to power in 2010 after two terms of scandal-filled Socialist rule.
Fidesz won a two-thirds majority in 2010 and 2014, but lost it in by-elections in 2015.
Mr Orban campaigned heavily on his unyielding anti-migration policies. He repeated his theory of a conspiracy between the opposition and the United Nations, the European Union and wealthy philanthropist Soros to turn Hungary into an "immigrant country," threatening its security and Christian identity.
The government has already submitted a "Stop Soros" package of legislation that it would easily be able to pass if Fidesz's obtains a two-thirds majority in parliament. Government spokesman Zoltan Kovacs said the bills are designed to close "legal loopholes" allegedly exploited by civic groups that advocate for asylum-seekers.
"So-called NGOs... are helping illegal immigration happen," Mr Kovacs said.
Government influence on the media was palpable in Sunday's broadcast by state television M1 news channel, where reports highlighting the negative effects of migration dominated the programming.
On Origo.hu, a formerly independent website now owned by government allies, stories promoted Mr Orban while also focusing on migration. The headlines included "Migrant gangs fought in England," They can't stand it anymore in Sweden: They've had enough of migrants", and "A migrant in underpants beat a German retiree half to death".
Hungarian election officials said voter turnout was high and had exceeded participation in the 2014 balloting 90 minutes before polls closed. Numerous polling places remained open past closing time to accommodate long lines of people waiting to cast ballots.
While Mr Orban's win was undeniable, the exact size of his margin of victory was not clear early on Monday due in part to Hungary's complex electoral system, in which voters cast ballots for both an individual candidate in their region and another for a party list.
Final election results are expected by April 27.