NATO said on Thursday that it was \"deeply concerned\" about the recent violence in northern Kosovo, which has seen NATO soldiers wounded by ethnic Serbs.\"(We) are deeply concerned about the recent developments in the northern part of Kosovo, which we continue to monitor carefully,\" NATO ambassadors said in a statement after a meeting with other representatives of contributing nations to the KFOR mission in Kosovo.\"The use of violence against KFOR is unacceptable and we deplore it...We urge all parties to exercise restraint and cooperate fully with all international actors on the ground to ensure freedom of movement without delay,\" the statement said.Tensions in northern Kosovo rose over the summer when Kosovo authorities ordered special police units to take over two border crossings with Serbia, only to meet strong resistance of local Serbs who set a security border post on fire and blocked the roads.In an attempt to dismantle the barriers which often led to clashes with Serbs, two NATO soldiers were shot and wounded during on Monday.Serbian President Boris Tadic on Tuesday urged NATO to refrain from violence against local Serbs, while calling on the Serbs to remove the barricades themselves, saying any escalation of violence was not in their interests.NATO welcomed Tadic\'s remarks, but stressed that it \"must be followed by concrete actions.\"KFOR has been deployed since June 1999 following the NATO bombing campaign against Yugoslavia. NATO members have slashed the troops in Kosovo from over ten thousands to 5,872 in August this year.However, German Defense Minister Thomas de Maiziere suggested on Wednesday that NATO may no longer reduce Kosovo troop level in view of the recent events.