Belgrade denies US claims of Serbian military mobilisation near Kosovo

The United States has urged Belgrade to pull its forces back from the border with Kosovo after detecting what it called an "unprecedented" Serbian military build-up, a claim rejected by Serbian President Aleksandar Vucic.

Serbia deployed sophisticated tanks and artillery on the frontier after deadly clashes erupted at a monastery in northern Kosovo last week, the White House warned.

"We are monitoring a large Serbian military deployment along the border with Kosovo," White House National Security Council spokesman John Kirby told reporters on Friday.

"That includes an unprecedented staging of advanced Serbian artillery, tanks, mechanised infantry units. We believe that this is a very destabilising development."

US Secretary of State Antony Blinken had telephoned Serbian President Aleksandar Vucic to urge "immediate deescalation and a return to dialogue," Kirby said.

Claims rejected

Serbia's leader Vucic has denied there had been a recent build-up rejecting claims that his country's forces were on alert.

"I have denied untruths where they talk about the highest level of combat readiness of our forces, because I simply did not sign that and it is not accurate," Vucic told reporters.

"We don't even have half the troops we had two or three months ago."

Serbia said Wednesday that the defence minister and head of the armed forces had gone to visit a "deployment zone" but gave no further details.

The violence - in which a Kosovo police officer and three Serb gunmen were killed - marked one of the gravest escalations for years in Kosovo, a former Serbian breakaway province.

Boosting NATO force

The NATO peacekeeping force known as KFOR would be "increasing its presence" following the attack, Kirby added.

In Brussels, NATO chief Jens Stoltenberg confirmed that the US-led alliance was ready to boost the force to deal with the situation.

In the north of Kosovo, where the Serb minority is concentrated, KFOR has decided to "increase its presence and activity", added a NATO official who requested anonymity.

He added that KFOR was prepared to make "further adjustments" if necessary to enable it to fulfil its peacekeeping mandate.

Kosovo broke away from Serbia in a bloody war in 1998-99 and declared independence in 2008 - a status Belgrade and Moscow have refused to recognise.

It has long seen strained relations between its ethnic Albanian majority and Serb minority, which have escalated in recent months in northern Kosovo.