Police, who investigate suspected terrorism, are in charge of a probe into the matter.
Senior members of President Sarkozy's UMP party were sent the threatening letters and so were three French cabinet ministers.
Among the leading politicians, who received the death threats, were French Justice Minister Rachida Dati and former PM Alain Juppe, as well as Interior Minister Michele Alliot-Marie and Culture Minister Christine Albanel.
The letters are said to have had 9mm or .38-calibre bullets packed in with them.
The Associated Press has issued a report stating that the threatening letters mention a "Cell 34",1,000 combatants, and claim that those politicians who received the threats have made fascist laws.
The letter ends with the following words: "This letter is the last. There will be a black out. Total silence."
Where the letter came from is at present unknown.
