The bridge has been the scene of frequent clashes since the 1999 war between Serbian forces and Kosovo's ethnic Albanian majority, which left 13,000 dead and ended after a US-led NATO bombing campaign.

Kosovo government officials have called for the opening of the bridge in the northern city, with Prime Minister Albin Kurti saying last week the crossing "must be opened" during a meeting with Western ambassadors.

Protestors carried Serbian flags and listened to the country's national anthem as they rallied near the bridge and slammed Kurti's government.

"For Serbs, this bridge here is a symbol of survival," said local judge Nikola Kabasic.

"Pristina wants to reopen Pandora's box," said another protestor who asked not to be named.

On Tuesday, the NATO-led peacekeeping force KFOR said it would intervene if Kosovo authorities sought to open the bridge.

KFOR maintains a strong presence in Mitrovica and regularly patrols the area around the bridge over the Ibar River that has been closed to cars for years.

The statement followed a recent visit to the bridge by members of the ethnic-Albanian-dominated governing cabinet, who were overseeing "an imminent technical inspection" of the area.

The KFOR statement came a day after Kosovo authorities raided at least nine Serbian post office branches near its northern border with Serbia.

Serbian post offices in Kosovo have long been used to receive funds, including pensions, and transfer money to financial institutions in Serbia.

Serbia-Kosovo tensions have simmered for months following the introduction of a rule this year that made the euro the only legal currency in Kosovo and effectively outlawed use of the Serbian dinar.

The move angered Belgrade, which continues to finance a parallel health, education and social security system for the Serbian minority in Kosovo.

Animosity between Kosovo and Serbia has persisted since the war between Serbian forces and ethnic Albanian insurgents in the late 1990s.

Kosovo declared independence in 2008, a move that Serbia has never acknowledged.