Hungary's far-right Jobbik party has sparked criticism after holding a political rally inside a former synagogue in the town of Esztergom.
Jewish groups called Friday's event "disgusting", saying it was "insulting to the memories" of Holocaust victims.
Jobbik leader Gabor Vona insisted his party did not want to "provoke anyone, including the Jewish community".
The party, which purports to protect Hungarian values and interests, is the third largest in parliament.
It regularly issues anti-Semitic statements.
Around 100 protesters gathered with candles outside the police-guarded building, which is now being used as a cultural centre.
Some wore a yellow star pinned to their coats.
The demonstrators tried to form a human chain to prevent Jobbik supporters from entering the building, but were hindered by security forces.
"It is a perversion from Jobbik to organise a forum at a former synagogue," protest leader Agnes Drelyo said.
Inside the cultural centre, Mr Vona told supporters that he had "nothing to be ashamed of".
"As a legal party which won the votes of around one million people in 2010, we have as much right as anyone to hold an event here," he said.
Meanwhile, the mayor of Esztergom said she had asked Jobbik to choose another venue, but had no authority to block the party from holding a rally in the old synagogue.
Some 500 Jews were deported during World War Two from Esztergom, which lies 50km (31 miles) north of the capital, Budapest. Most died in concentration camps in 1944.
Jobbik became Hungary's third-largest party after it won 16% of the vote in the 2010 election.
Its deputy group leader, Marton Gyongyosi, caused outrage two years ago when he said officials of Jewish origin should be listed because they might be a "national security risk".