 Complete the following phrase:  Clashes between the Republic of Kosovo and ethnic Serbs in northern Kosovo began on 25 July 2011 when the Kosovo Police crossed into the Serb-controlled municipalities of North Kosovo, in an attempt to control several administrative border crossings without the consultation of either Serbia or KFOREULEX. Though tensions between the two sides eased somewhat after the intervention of NATOs KFOR forces, they continued to remain high amid concern from the European Union, who also blamed Kosovo for the unilateral provocation. On 19 April 2013, 