Bullets have been mailed to the Tokyo headquarters of the ruling Democratic Party of Japan and TV Asahi Corp. with the envelope received by the DPJ containing a letter demanding that scandal-hit DPJ Secretary General Ichiro Ozawa quit, investigators said Tuesday.
The envelopes bore no sender names and were apparently posted in Okayama Prefecture, the police said.
The bullets are 9 mm in diameter.
The letter to the DPJ criticizes Ozawa's political and diplomatic stances and warns other party lawmakers to "be on their guard," the police said.
The envelope sent to TV Asahi contained a letter blasting media companies in general and criticized reports about the ruling party, according to the television station and police.
Ozawa has been under fire over alleged mishandled political funds.