There have been clashes in Prague between neo-Nazis and protesters trying to block their right-wing march.
Some of the protesters donned Jewish Star of David badges
More than 1,000 people rallied in the Czech capital's old Jewish quarter to try to stop the march by members of the Young Nationalist Democrats (MND).
The march was planned for the anniversary of the 1938 anti-Jewish purge known as Kristallnacht.
Police managed keep most of the 400 right-wing marchers and the anti-Nazi demonstrators separate.
But there were scuffles in side streets near the Jewish quarter and at least one person was injured, witnesses said. Police arrested several of the right-wing marchers.
Anarchists in other parts of the city also clashed with police.
In the end, the handful of Neo-Nazis who managed to evade the police patrols found they were heavily outnumbered by a large crowd of anti-fascist protesters, says the BBC's Rob Cameron in Prague.
A shot was apparently fired at a crowd outside the city's law faculty, leading to skirmishes, he adds.
The MND said the march was officially a protest at the Czech military presence in Iraq.
It had been banned after a series of court judgements, but the neo-Nazis repeated their calls to be allowed to demonstrate, saying they had no other way of expressing their political views.
Some of the MND skinheads arrested were armed with batons, truncheons and home-made Molotov cocktails, reports said.
Scuffles broke out between the rival groups
"The march [by the extreme right] was unacceptable," Prague's mayor Pavel Bem told the AFP news agency. "We need to cultivate the national memory to avoid what happened in the past."
Czech President Vaclav Klaus also condemned the MND march.
Some of the anti-fascist protesters wore a yellow Star of David, while others carried red flags and wore slogans reading "Never Again".
They gathered in front of a Prague synagogue near a museum dedicated to the memory of some 77,000 Jewish victims of the Holocaust who came from the former Czechoslovakia.
"I came because I don't like these idiots with their shaved heads," one demonstrator, a 17-year-old named Vera, told AFP.
On Friday, Czech tour operators warned tourists to keep out of central Prague and said organised tours would not travel into the area.
There were reports that busloads of German far-right supporters had been detained at the Czech border by police.