At least 22 people, including 13 police officers, have been injured in protests in the Macedonian capital, Skopje, police have said.
The protests, which erupted on Friday evening and continued overnight, were started by ethnic Macedonians angry at the appointment of a new defence minister - an ethnic Albanian and former rebel commander in the 2001 conflict which pitted Macedonian's two main ethnic groups against one another.
Ethnic Albanians have now staged a counter-protest in the capital.
Both protests turned violent, with ethnic Macedonians and Albanians taking turns to scuffle with police but, so far, not with one another.
Talat Xhaferi was named defence minister two weeks ago, sparking protests which then escalated.
Police said 18 arrests have been made so far, and five of those arrested are minors.