A deadly clash in Kosovo about a week ago triggered one of the gravest escalations in the former breakaway province in years.

The number of troops was cut from 8,350 to 4,500, Serbian army chief of staff General Milan Mojsilovic said.

"It means the regular number of troops" in the area, he added. "The operational regime of the (Serbian army) units... tasked with securing the administrative line with Kosovo is back to normal."

Around 30 gunmen were involved in a shootout with Kosovo police in a north Kosovo village in late September, killing one officer.

It was one of the most serious escalations in years in the former Serbian province, with ethnic Albanian-majority population.

Three Serb gunmen were also killed in the hours-long shootout in the village of Banjska on September 24, after they ambushed a patrol and latter barricaded themselves at an Orthodox monastery near the northern border with Serbia.

On Friday, the United States called on Serbia to pull its forces back from the border with Kosovo after detecting what it called an unprecedented Serbian military build-up.

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

Mojsilovic on Monday voiced surprise over a "deep concern of some" regarding Serbian forces deployed during what he called "security crisis".

In December 2022 and May 2023, during "similar security crises", Serbia deployed 14,000 troops in the area, he said.

At the time, unlike a week ago, they were on the "highest level of alert", Mojsilovic added.

Kosovo declared independence from Serbia in 2008, a move Belgrade as well as its allies Beijing and Moscow have refused to recognise.

Kosovo has long had strained relations between its ethnic Albanian majority and Serb minority, which have escalated in recent months in Kosovo's north.

Despite years of European Union-sponsored talks between Kosovo and Serbia on normalising ties, little progress has been achieved.