The men came originally from Krusevac and Aleksandrovac - two towns in southern Serbia which have seen anti-war demonstrations.

Some of the reservists say other soldiers are also considering leaving their posts.

Up to 500 soldiers have deserted in Kosovo, the US State Department said.

Quoting "credible reports" without identifying them, spokesman James Rubin said the desertions were among "increasing signs that Belgrade is feeling the heat" of Nato air strikes.

The Yugoslav army has said it plans to charge organisers of the demonstrations in Krusevac and Aleksandrovac with treason.

The two towns are controlled by the Democratic Party, whose Belgrade offices were stoned and daubed in graffiti by supporters of President Slobodan Milosevic on Wednesday.

Protesters in the southern towns are reported to have displayed placards calling for "sons not coffins" in the towns.

BBC World Affairs Editor John Simpson: "We are entering a very sensitive phase"

Many were said to be the mothers and wives of conscripts serving in Kosovo.

A Nato source said: "The report we have says the conscripts heard about the treatment of their families, got in their trucks and after some scuffles and headed for home."

BBC World Affairs Editor John Simpson said the men have been told they will be able to hand over the weapons and uniforms and receive a certificate saying they took part in the war.