Serbian police have detained a 17-year-old migrant from Afghanistan suspected of stabbing to death another Afghan national in central Belgrade.

Police said on Thursday they are still searching for another 17-yar-old migrant also suspected of taking part in the attack late on Wednesday in the Serbian capital.

Clashes often happen among thousands of migrants who have been stuck in the Balkans while looking for ways to move toward Western Europe.

Police in northwestern Bosnia say tensions persist there among migrants who clashed early on Wednesday in an asylum center in the town of Velika Kladusa. About 100 migrants were involved in the fight that left scores injured, including three policemen.

Spokesman Ale Siljdedic says police are on standby because "the situation among them could escalate at any moment."