Budapest (AFP) - Hungarian Prime Minister Viktor Orban warned Friday that opposition parties, buoyed by a shock by-election win, are now a "serious challenge" to his ruling rightwing Fidesz party.
He also doubled down on his main campaign theme ahead of a general election next month, saying that the opposition could turn Hungary into a "country of immigration" if he loses.
Polls had given the fiercely anti-immigration Fidesz party a lead of around 30 percentage points over its nearest rival.
But a local by-election on Sunday saw a landslide victory for an independent candidate backed by opposition parties from the left to the far-right.
The rare show of opposition unity was a "test-run" for the parliamentary election April 8, Orban said.
Orban has responded by renewing his focus on his opposition to immigration, his main campaign theme.
"Ultimately there will be single pro-immigration candidates facing anti-immigration ones supporting the national government," he said in a public radio interview.
The surprise win has fuelled optimism among opposition parties that Orban could even be toppled, an unthinkable scenario before Sunday.
"If parties work together, no electoral district is unwinnable," the Socialist party's prime ministerial candidate Gergely Karacsony told AFP Thursday.
Since 2015 Orban has mounted campaigns accusing American billionaire George Soros of backing the opposition and orchestrating mass migration from Muslim countries into Europe.
"If (migrants) get in, they can't be removed, if toothpaste comes out of the tube no one can get it back in," Orban said.
Migrant "no-go zones" could be created in Hungarian cities, he said in the northeastern city of Miskolc Thursday.
Orban said Miskolc "had already experienced" the impact of migration into the city from elsewhere in Hungary, appearing to refer to the ethnic Roma community, the country's largest minority.
Gabor Varadi, a Roma politician in Miskolc, called on Orban to apologise to his community for "stigmatising" them.
"Everything starts with words. So let's not be surprised if Roma are attacked after this," Varadi told local media.
Calling Roma "who have been in Hungary for over 600 years 'immigrants' is unacceptable incitement," he said.