The second man was later released and police said he was not related to the Ivanovic case, though he was accused of possessing an illegal weapon. Prosecutor Syle Hoxha said the arrested police suspect is accused of "hiding evidence and not carrying out the required duties."
Kelani said police are still working to arrest the other police officer. In August, Kosovo issued an international arrest warrant for Milan Radoicic, deputy leader of the Belgrade-supported Serbian List party, suspected of involvement in Ivanovic's killing and highly influential among the ethnic Serb minority.
The prosecutor said the arrested officer and the one at large "have been under the influence of Radoicic's group." None of the identified suspects is believed to have actually carried out the slaying.
Wednesday's arrests provoked criticism in neighboring Serbia. Politician Milovan Drecun said it was a public show designed to put pressure on the Belgrade-supported Serbian List party, which won 10 seats in Kosovo's snap election earlier this month.
Kosovo declared independence from Serbia in 2008, but Belgrade refuses to recognize it.