Police are looking for Eden Gacic who is suspected of killing a grocery shop owner new Konjic, a week ago, and shooting a policeman on Saturday in Suhodol.
Gacic, 42, has previously served two prison terms for murder and was released in 2017, after serving two-thirds of his 20 year sentence.
He was convicted then of killing his mother, and a man who served with a battalion of Muslim volunteers during the 1992-95 war in Bosnia.
According to Bosnian media, Gacic served in the same unit as the man he killed, which fought alongside Bosnian army soldiers under the country’s wartime Muslim-led government.
Aljosa Campara, the country’s interior minister, said: “We are checking any information we get. All police agencies have been engaged.
“We are doing all we can to protect the citizens.”
Police said 1,200 officers have been deployed in the manhunt and they are prepared to ask the army to step in if necessary.
Heavy snow has made the search in mountainous regions more difficult.
Bosnians have expressed fears about the gunman on the loose.
One villager in Suhodol admitted people may flee, saying: “Of course I am scared, I won’t just sit here and wait for him to kill me.”