BELGRADE, May 29. /TASS/. The NATO-led international security force in Kosovo (KFOR) has failed to defend Serbs in Kosovo and Metohija, in spite of the guarantees, Serbian President Aleksandar Vucic said on Monday.

"Despite the guarantees, KFOR troops failed to defend Serbs and failed to prevent the seizure of municipalities and violence," he said in an address to the nation.

Earlier on Monday, KFOR forces blocked access to the buildings housing the municipal administrations of the cities of Zvecan, Zubin Potok, and Leposavic and did not let Serbs in.

On May 26, Serbian President Aleksandar Vucic called on NATO to take urgent measures to put an end to violence against Serbs in Kosovo after the Kosovo police seized administrative buildings in four municipalities in northern Kosovo and Metohija to make its possible for the new mayors of the four municipalities, who were elected despite nearly the entire Serb population boycotting the elections, take their offices. In response to the actions of the Kosovo authorities, Belgrade put its army on high alert and deployed troops to the administrative border with Kosovo.