The family of three American citizens killed during fighting in Serbia in 1999 says the Balkan country's prime minister has failed on his promises to put the suspects to justice.

The Bytyqi brothers left New York to fight with ethnic Albanian rebels against Serbia's rule in Kosovo. They were arrested when they strayed into central Serbia. Their bodies were discovered in a trash-filled mass grave in 2001.

In an email to The Associated Press, the family's lawyers say Tuesday "despite repeated requests, the Bytyqi family has not been given updates on any future plans to move the case along." They say Serbian Prime Minister Aleksandar Vucic "has lied multiple times to the family of three murdered American citizens. He should be held accountable."

Kosovo declared independence from Serbia in 2008.