Riot police Tuesday broke up a scuffle between scores of Slovaks and Hungarians in an ethnically tense border town, the Slovak news agency TASR reported. Three people were detained, but apparently no one was injured during the confrontation in Komarno, a town of 40,000 on Slovakia's bank of the Danube River, about 100 kilometres southeast of Bratislava, DPA reported. The trouble began during a nationalist street rally by about 50 Slovaks who waved flags and chanted slogans to mark Tuesday's state holiday. Some were wearing black shirts, the report said. The report said a clash with clubs broke out between young men from the rally and a group of about 40 ethnic Hungarians, but police were prepared and managed to separate the groups. Komarno and its smaller sister town on the Hungarian side of the river, Komarom, were united before a 1920 treaty divided the city between the former Czechoslovakia and Hungary. Today most residents of the Slovak town are ethnic Hungarians. Ethnic tension between Slovaks and Hungarians is common in the Danube valley. Reducing the tension was one objective of a European Union-funded river bridge completed four years ago to link Sturovo, Slovakia, and Esztergom, Hungary, about 50 kilometres downstream from Komarno.