Roma in Hungary's second largest city simultaneously held a counter-rally rejecting what they said were typical right-wing slurs while police kept the two sides apart, preventing serious clashes.
"Jobbik will help those who build Hungary, no matter their colour," party leader Gabor Vona told about 3,000 supporters. "But we will go after those who destroy and won't let them be!"
The protests underscored increasing tensions in recession-hit Hungary, which had asked for a financing deal with the International Monetary Fund and the European Union and whose conservative government has announced unpopular austerity measures to cut the budget deficit.
"I can't live in this area anymore like this," said Jobbik protestor Tamas Kormendi, 25, who is unemployed.
"Not a day goes by without some incident that turns my stomach. These gypsies live like pigs and I swear they like it. Well, they will not like it for long if it's up to me."
The leaders of the Roma community rejected the accusation that they were to blame for crime and safety problems.
Jobbik, which holds 45 of 386 Parliament seats, has capitalised on widespread public resentment of Hungary's estimated 700,000 Roma, whom it has vilified for years.
The party says budget cuts left no room to pay for public safety in parts of the country, including Miskolc - a former communist industrial centre - 180 km east of Budapest.
The city's ex-communist Avas housing projects, home to about 40,000 people, have seen mass immigration of destitute Roma from the countryside, where living conditions are often rustic.
Long-time residents have shunned the new Roma occupants, many of whom have large families crammed into tiny flats.
The protestors marched around the housing project with torches, intermittently bellowing slogans such as "Gypsy crime! Gypsy criminals!"
About 1,000 Roma marched in the afternoon and held a rally in the city centre. There was no friction between the protests which were in separate parts of town, heavily guarded by police.