Swedish police arrested more than 20 people Saturday as they tried to keep neo-Nazis and anti-fascists from clashing in Sweden's second largest city.

The Nordic Resistance Movement (NMR), a right-wing extremist group that is openly anti-Semitic, received permission from police to hold their rally on Yom Kippur, the holiest day of the Jewish calendar.

The NMR originally sought to march past a Jewish synagogue but a court rejected their proposed route, and shortened it to little more than half a mile (1 kilometer).

About 600 people wore all-black outfits as they marched in formation. Some waved the movement's green and white flag, and some wore helmets and carried shields, as they went through Goteborg about 250 miles southwest of the capital Stockholm.

Authorities posted fliers ahead of the rally warning demonstrators against behaving like German Nazi's "National Socialist demonstrations in the 1930s and 1940s."

The end time for the march was also scaled back by one hour to prevent potential clashes with attendees of a nearby football game.

Neo-Nazis and anti-fascists

Anti-fascists, the counter-demonstrators, tossed fireworks and made several attempts to break through police lines in an apparent effort to confront NMR members who also tried to get past riot police. Some were arrested and charged with rioting, according to police.

Among those arrested was one person accused of kicking a policeman in the face and two others who were detained for carrying knives.

"Stones, bottles and sticks were also thrown at us," police spokesman Hans Lippens said.

Neo-Nazis wielding transparent shields and their green and white flags clash with police

Riot police eventually encircled the NMR in a city square, preventing them from finishing their march. Officials said the police action was intended to keep the neo-Nazis and anti-fascists from a direct clash. The number of anti-fascist protesters was not immediately clear, but pre-march estimates indicated they could outnumber their neo-Nazi counterparts by as much as 10-1.

The NMR subsequently demanded that their leader Simon Lindberg be released from police custody before they would leave the square.

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About 20 people, mainly from Denmark and Germany, were detained as they arrived in Sweden ahead of the rally.

Law enforcement officials anticipated violence and called in police reinforcements from across Sweden before the protest. They alsoconverted a police garage into a temporary detention center, and added 350 beds.

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Goteborg was rocked by violent protests during a European Union summit in 2001.

bik/jlw (AP, Reuters)