NOVI SAD (AFP)---Serbian police arrested about 30 neo-Nazis, including Slovak nationals, Sunday after they attacked anti-fascist activists in the northern city of Novi Sad.

Officers moved in as the neo-Nazis, who had gathered despite a ban on their planned demonstration, threw bottles and stones towards the anti-fascists as they marched to the town centre.

The neo-Nazi group ’Nacionalni Stroj’ -- "National Rank" in Serbian -- had called for a march for Serbian unity.

It was banned after pressure from Serbian political groups and the World Jewish Congress.

The anti-fascists nevertheless went ahead with their counter-demonstration, which was organised at the initiative of a number of political parties and organisations.

Among the neo-Nazis arrested were 11 Slovak nationals, some of whom had Nazi propaganda and swastikas, the Tanjug agency reported, citing police sources.

In Belgrade meanwhile, eight Bulgarian neo-Nazis were arrested.

Riot police were out in force in Novi Sad, which is the main city in ethnically mixed Vojvodina province.

Members of the Serbian neo-Nazi group, including 31-year-old leader Goran "The Fuhrer" Davidovic, have already been jailed for spreading racial hatred in Novi Sad.

The group was found guilty of having disrupted a Novi Sad university lecture about the threat of fascism in November 2005.

Earlier that year, anti-Semitic posters and graffiti signed by the group appeared in Novi Sad and Belgrade.