A death threat has been issued against a vocal critic of Japan's newly-launched security legislation, a media report said.
Meiji Gakuin University student Aki Okuda is a key member of a group opposed to the laws that were enacted last month, NHK news agency reported.
The university and other sources said a letter addressed to Okuda was received on September 24 which threatened to kill the activist and his family members.
Okuda and other students launched the protest group called Students Emergency Action for Liberal Democracy also known as SEALDs in May.
SEALDs organised protests against the Japanese government's security legislation outside the parliament building. Okuda also appeared at a parliament hearing to share his views.
Okuda said he has filed a complaint. He said he did not understand why his family has been threatened in addition to himself.
Meiji Gakuin University said in a statement that it regards the threat as an unforgivable act against freedom of speech. The university is taking measures to ensure the safety of its students, teachers and officials.