A unique art show is under way at a small Tokyo gallery displaying 40 paintings by 26 prisoners, including current and executed death row inmates.

"As the prisoners are under extreme restraint, their imagination has been well-honed," said Hiroshi Matsuhashi, owner of the TEN gallery. "I expect people to find their wordless messages, expressed in their work, as they are."

The works on display include those by Toshihiko Hasegawa, who was hanged in 2001 over a murder-for-insurance case despite the plea of the victim's family not to execute him, and former Japanese Red Army leader Fusako Shigenobu, who is serving a 20-year prison sentence.

Among the three paintings by Hasegawa is a monochrome snowy landscape, while Shigenobu, who was convicted over the seizure of the French Embassy in The Hague in 1974 and for violating the passport law, has contributed still lifes.

Two paintings by Sadamichi Hirasawa, who was sentenced to death over a 1948 mass poisoning known as the "Teigin Incident" and died in a prison hospital aged 95 after pleading his innocence, are also on display, depicting a flower against the backdrop of iron bars.

Hirasawa, an award-winning painter before his arrest, continued painting in his prison cell and is believed to have left thousands of works.

Another inmate, whose death sentence has already been finalized, has contributed a large ink-wash painting of a carp, which won an award in a public contest.