Orban, who is already the country's longest serving-leader since the fall of communism in 1989, has long been a thorn in the side of the European Union with Sunday's vote likely to mean further clashes between Budapest and Brussels over the next four years.

The result is projected to keep the Fidesz party in power with a two-thirds majority — a key "supermajority" level which allows constitutional changes.

With around 93 percent of the ballots counted, Hungary's National Election Office said Orban's ruling administration had secured almost half of the vote on Sunday.

Hungarian Prime Minister Viktor Orban has secured a third successive term in office after his right-wing Fidesz party won by a landslide in parliamentary elections. With around 93 percent of the ballots counted, Hungary's National Election Office said Orban's ruling administration had secured almost half of the vote on Sunday. The result is projected to keep the Fidesz party in power with a two-thirds majority — a key "supermajority" level which allows constitutional changes. The 54-year-old incumbent, who had built a fence on Hungary's southern border during the 2015 migration crisis, campaigned for re-election on an anti-immigration and protectionist message once again. He has also pledged to cut income taxes and pass pro-economic growth policies. Speaking to supporters outside the Fidesz election headquarters in Budapest shortly before midnight local time, Orban said citizens of the central European nation had given themselves an "opportunity to defend themselves."

Migration: A fear of the 'unknown'

The Fidesz party improved significantly on its performance in 2014, gaining a further 5 percent share in the popular vote this time around. Orban's campaign was thought to have been aided by an improving economic outlook, his party's stringent control over state media and deep divisions among opposition parties. "What we can see is that Viktor Orban won this election due to only one issue — and this is clearly migration," Andras Biro-Nagy, political analyst at Policy Solutions, a Hungarian think tank, told CNBC's "Squawk Box Europe" Monday.

Hungarian Prime Minister Viktor Orban addresses the supporters after the announcement of the partial results of parliamentary election in Budapest, Hungary, April 8, 2018. Leonhard Foeger | Reuters

Biro-Nagy said that as relatively few people had been allowed to emigrate to Hungary in recent decades, the migration issue was an "unknown thing" for a large portion of the electorate. "For the vast majority of the population, (immigration) is seen as a threat to the cultural identity of the country. This is why economic arguments like potential GDP growth due to immigration simply do not matter," he added. Voter turnout had soared to near-record highs of 69 percent — an outcome which analysts had anticipated could boost the chances of the prime minister's opponents. However, with almost all of the ballots counted, the right-wing Jobbik party accrued 20 percent of the vote. Meanwhile, the Socialist party appeared to finish third with 12 percent while the LMP — Hungary's main Green Party — finished fourth with around 7 percent of the vote. Leaders of the second and third-placed parties have since announced their resignation.

'Mass immigration rejected once again'

Orban, who is already the country's longest serving-leader since the fall of communism in 1989, has long been a thorn in the side of the European Union with Sunday's vote likely to mean further clashes between Budapest and Brussels over the next four years.

Mehmet Yilmaz/Anadolu Agency/Getty Images