Belgrade media reported that five former or serving Serb policemen were arrested on Sunday, including a police colonel serving as deputy commander of the gendarmerie.

A spokesman for the war crimes prosecutor declined to confirm whether the suspects were policemen.

"The four will be handed over to the investigative judge today," he said.

Two former Serb policemen went on trial in Belgrade in November charged as co-perpetrators in the murder of Argon, Mehmet and Ilaj Bytyci, ethnic Albanian brothers with US citizenship.

The brothers had strayed from Kosovo into Serb-controlled territory in late June 1999 days after NATO occupied Serbia's southern province following 78 days of bombing to drive out Serb forces accused of atrocities in a two-year war with guerrillas.

They were imprisoned for 17 days for illegal entry. On their release they were picked up by secret police, taken to another location and shot dead, their hands tied behind their backs with wire, according to the indictment.

Their bodies were found only in 2001 when reformers who had ousted late president Slobodan Milosevic in 2000 unearthed mass graves in Serbia containing the bodies of over 800 Kosovo Albanians. They were killed in the province and trucked north to conceal evidence of atrocities.

The police chief at the time of the killings, Vlastimir Djordjevic, is suspected of having ordered the Bytyci killings. He has been indicted by the U.N. war crimes tribunal in The Hague and is believed to be hiding in Russia.