Nine Japanese companies, including drugmakers and a newspaper, have received blackmail letters containing white powder suspected to be cyanide, police and local media said Sunday.

The letters were sent under the names of executed members of the Aum Shinrikyo -- the Japanese doomsday cult behind the deadly 1995 sarin gas attack in Tokyo -- and demanded 35 million won ($31,000) in bitcoins, a police spokesman told AFP.

"Major pharmaceutical and other companies... received envelopes with threatening letters and a powdery substance" suspected to be cyanide, he said, without identifying the companies.

"I will make fake medicine containing potassium cyanide and distribute it," the letter said, according to the spokesman, and warned "a tragedy will happen" if the money was not transferred by February 22.

Read more: AFP