The Bytyqi brothers -- Ylli, Mehmet and Agron -- were detained by Serbian police in June 1999 shortly after the end of the war between Serb forces and ethnic Albanian separatists in Kosovo, where the three had roots.

Two years later, their bodies were found in a mass grave in a special police base in eastern Serbia.

No one has ever been convicted over the crime, though two Serb police officers were acquitted in a 2012 trial, drawing concern from the US that the case would remain unsolved.

On Tuesday, the US State Department said that Goran Radosavljevic, a well-known former police commander now in his 60s, was banned from the US because he has been "credibly implicated" in the killing of the Bytyqi brothers.

Known by his nickname 'Guri', Radosavljevic was a commander of a unit in Petrovo Selo, a police training camp where the mass grave containing the bodies of the Bytyqi brothers, and 71 others, were later found.

He later went on to join the current ruling party in Serbia, the Serbian Progressive Party (SNS).

According to local media, he has previously denied any involvement in the murders.

Radosavljevic's wife and daughter are also banned from the country, the State Department said.

More than 13,000 people -- mostly ethnic Albanians -- were killed in the 1998-99 war that paved the way for Kosovo to declare independence a decade later.

After the fall of former Serbian strongman Slobodan Milosevic in 2000, the bodies of more than 800 Kosovo Albanians were exhumed from mass graves around Serbia.

Serbia has never recognised Kosovo's independence and still considers the former province a renegade territory.