Feb 10 (Reuters) - Greece's largest police union has threatened to issue arrest warrants for officials from the country's European Union and International Monetary Fund lenders for demanding deeply unpopular austerity measures. In a letter obtained by Reuters on Friday, the Federation of Greek Police accused the officials of "...blackmail, covertly abolishing or eroding democracy and national sovereignty" and said one target of its warrants would be the IMF's top official for Greece, Poul Thomsen. The threat is largely symbolic since legal experts say a judge must first authorize such warrants, but it shows the depth of anger against foreign lenders who have demanded drastic wage and pension cuts in exchange for funds to keep Greece afloat. "Since you are continuing this destructive policy, we warn you that you cannot make us fight against our brothers. We refuse to stand against our parents, our brothers, our children or any citizen who protests and demands a change of policy," said the union, which represents more than two-thirds of Greek policemen. "We warn you that as legal representatives of Greek policemen, we will issue arrest warrants for a series of legal violations ... such as blackmail, covertly abolishing or eroding democracy and national sovereignty." The letter was also addressed to the European Central Bank's mission chief in Greece, Klaus Masuch, and the former European Commission chief inspector for Greece, Servaas Deroose. Policemen have borne the brunt of the anger of massed protesters who frequently march to parliament and clash with police in riot gear. Chants of "Cops, pigs, murderers!" are regularly hurled at policemen or scribbled on walls. Thousands turned out on Friday for the latest protest in Athens, this time against new austerity measures that include a 22 percent cut in the minimum wage. A police union official said the threat to 'refuse to stand against' fellow Greeks was a symbolic expression of solidarity and did not mean police would halt their efforts to stop protests getting out of hand. (Reporting by Lila Chotzoglou, Writing by Deepa Babington, editing by Tim Pearce)