(Recasts, adds NATO spokesman's comments in final two paras)

BELGRADE, March 17 (RIA Novosti) - Over 100 people have sustained injuries in clashes between ethnic Serbs and police in northern Kosovo on Monday, Belgrade-based media said.

The violence in Mitrovica began when United Nations police and NATO-led KFOR troops launched an operation this morning to regain control of the UN court building, seized last week by Serbs.

As well as about 70 Serb civilians injured in the violence, eight French troops from the international NATO-led Kosovo Force (KFOR), 13 Ukrainian officers of the UN police force and 23 Polish policemen were also injured.

The people occupying the court building were former court employees who lost their jobs when Kosovo became a UN protectorate in 1999 after a NATO bombing campaign of Serbia to end a conflict between Serbs and ethnic Albanians. After forcing their way into the courthouse last Friday they hoisted two Serbian flags over the building.

UN mission spokesman Alexander Ivanko said the UN police force command decided to withdraw police from Mitrovica leaving the city, divided between ethnic Serbs and an Albanian majority, in charge of KFOR troops. He added that the UN mission is in talks with Belgrade and Serbian authorities in Mitrovica aiming to rectify the situation.

NATO spokesman James Appathurai told RIA Novosti on Monday that the alliance would reinforce the KFOR mandate.

He said NATO strongly condemns the rioting in Mitrovica, and called on all parties to show restraint.