The rally was held under the slogan "For Kosovo and Metohija in Serbia", with Kosovo Serbs underlining that they could not accept independence for Kosovo.
The protest, organised by the Serb National Council of north Kosovo, was the biggest Serb rally since 1999 and the arrival of the international mission to Kosovo, said Serb sources in the north of the province.
The protest was peaceful and was followed by a march to the bridge on the Ibar river, on the other side of which is the Albanian-populated part of Mitrovica.
The Serb National Council announced new protests in the next 10 days in various parts of Kosovo and subsequently in Belgrade.
The Albanian movement Self-Determination, which is led by Albin Kurti, called on Kosovo's citizens to take part in demonstrations in Pristina on Saturday in protest against Ahtisaari's plan and the resumption of negotiations with Belgrade on Kosovo's final status.
The radical National Movement for Kosovo's Liberation, which was illegal until 1999, today rejected Ahtisaari's plan in its entirety because it did not recognise the people's right to self-determination, a statement said.