BELGRADE, Serbia (AP) — The family of three American citizens slain after fighting in Serbia in 1999 has accused the Balkan country's authorities of refusing to bring the killers to justice despite repeated pledges to do so.

The Bytyqi brothers, Ylli, Mehmet and Agron, left their New York pizza business to fight with ethnic Albanian rebels against Serbia's rule in Kosovo. They were arrested at the end of the clashes in 1999 when they strayed into central Serbia. Their bodies were discovered in a mass grave in eastern Serbia in 2001.

In a statement issued on Monday, the 19th anniversary of the killing, the Bytyqi family said that President Aleksandar Vucic has repeatedly promised American officials that Serbia would solve the case, which has burdened relations between the two states.