Aleksandar Vucic told the Serbian parliament on Monday evening that "there is no evidence of who committed the murder" of Ylli, Agron, and Mehmet Bytyqi - US citizens of Albanian origin who were killed in Serbia in 1999.
Vucic said that without evidence, no one be arrested based "only on media reports and lawyers' claims", because "Serbia is a serious state".
The Higher Court in Montenegro on Thursday sentenced 13 people, including two Russian military intelligence officers and two opposition leaders, to up to 15 years in prison for staging an attempted coup in 2016.
They were found guilty of plotting to commit "terrorist acts" and undermine the constitutional order of Montenegro during the parliamentary elections in October 2016.
Serbian right-wingers have begun a concerted campaign against BIRN project coordinator Sofija Todorovic since she defended the rights of an ethnic Albanian baker in her hometown of Borca - himself the subject of nationalist attacks - sharing hate speech, insults and threats to her on social media and attempting to hack her account on Twitter.