The houses of local Albanians in that predominantly Serb populated part of the city were destroyed during the war in 1999.
About a hundred Serbs from the suburb of Brdjani tried to stop construction work on the Albanian houses, and then EULEX policemen threw teargas and shock grenades on the protesters, Serb sources from North Mitrovica reported.
After that, protesting Serbs dispersed but they announced the continuation of protests in the coming days.
According to the same sources, some of the shock grenades fell into the yards of Serb houses.
EULEX and Kosovo Mission forces have stepped up their presence in the area.
The protests started on Monday when local and international police forces in Kosovo clashed with some 100 local Serbs who were protesting against the reconstruction of Albanian-owned houses in that part of the city.
The Czech Presidency of the European Union said in a statement on Wednesday morning that the EU "is deeply concerned by the recent outbreak of violent protests resulting in a number of injured persons in Northern Mitrovica."
"The EU fully supports the actions of EULEX and KFOR in establishing the rule of law in Kosovo and in defending a safe and secure environment. The EU will press for anyone who endangers the lives of EULEX and KFOR personnel, as well as any other law-abiding citizens, to be brought swiftly to justice," the Czech Presidency said in the statement.
"The EU defends and supports people's right of return to houses and property that they legitimately own, regardless of their ethnic origins."
Kosovo President Fatmir Sejdiu accused Belgrade of orchestrating violent protests in Northern Mitrovica.
The Serbian minister in charge of Kosovo, Goran Bogdanovic, said that the reconstruction of Albanian houses on the so-called yellow line of demarcation could not be conducted without the consent of the Serb community.