The office of the Bosnian premier confirmed on Wednesday that three days ago they had received a letter with threats and reported it to the police.
The letter, marked by abusive language, says that Spiric should be punished for working against Bosnia and the Bosnian people.
The letter accuses the cooperation of "Ustasha from Herzegovina and the Chetniks who work against the Muslim people".
According to the Sarajevo-based Dnevni Avaz, the letter was reportedly sent from the southern city of Mostar.
The State Protection and Protection Agency (SIPA) head, Mirko Lujic said the police had been notified about the letter and that an investigation was under way to establish who sent it and how serious threats might be.
SIPA official Dragamn Lukac said that the head of the Bosnian government was one of the top state officials provided with maximum protection.
Following an analysis of how serious threats are, we will decide on some possible further security measures, Lukac told the Banja Luka-based "Nezavisne Novine" dialy, adding that Spiric's security was not in danger.