ATHENS (Reuters) - Greece is investigating threats against its foreign minister that authorities believe are linked to his attempts to resolve a long-standing name dispute with the neighboring state of Macedonia.

FILE PHOTO - Greek Foreign Minister Nikos Kotzias speaks during an interview with Reuters at the Foreign Ministry in Athens, Greece, January 31, 2018. REUTERS/Costas Baltas

A letter addressed to Foreign Minister Nikos Kotzias and received on Thursday said there were “three bullets” for him.

“It was threats to him and his family,” Civil Protection Minister Nikos Toskas told ANT1 TV on Friday. Toskas said that sending threatening letters to those who have been trying to settle a problem in a honest manner was “dangerous”.

Kotzias had received other threatening letters and calls in recent weeks, a government official said.

Kotzias is leading talks to resolve the dispute over Macedonia’s name, which has frustrated its ambitions to join NATO and the European Union since the 1990s, and said on Thursday that he would soon submit proposals.

Greece, which has its own region called Macedonia, has objected to its neighbor’s name since the small Balkan state broke away from Yugoslavia in 1991.

Greece argues that the use of the name, along with contentious articles in Macedonia’s constitution, imply territorial claims over Greek land.

Many Greeks feel passionately that there can be no deal including the term “Macedonia”, which for them is the name of the ancient kingdom ruled by Alexander the Great, and an integral part of their heritage.

Because of Greek objections, the Balkan state was admitted to the United Nations with the provisional name “The Former Yugoslav Republic of Macedonia” in 1993, and this remains its official title in international organizations.

Hundreds of thousands turned out at a demonstration on Jan. 21 in Thessaloniki, capital of Greece’s Macedonia region, to protest against any use of the name by the neighboring state, and a rally is scheduled for central Athens on Sunday.

Kotzias, who was an academic before joining the leftist-led government in 2015, in a tweet accused long-time adversaries, in which he also included some unnamed media, of being “the moral instigators of these threats against my life”.