Veljovic told Serbian Television contacts with the Croatian police began last night after leads indicated the possible perpetrator might be from or was hiding in Serbia.
He said both police forces wanted to solve the case, regardless of the perpetrator.
Croatian police received information about a person from Novi Sad who this summer wore a jersey of the football club Milan that was found in a backpack near the murder site and asked the Serbian police to check the person, the Croatian Interior Ministry said.