The Tokyo High Court dismissed an appeal Thursday by an Aum Shinrikyo defendant convicted of conspiring to build a plant to produce the nerve gas sarin, upholding a lower court-imposed, four-year prison term.

Presiding Judge Tadaharu Kanda turned down the appeal by Hiroyuki Okada, 35, whose lawyers claimed Okada's initial confession was not credible. Kanda said he did not think Okada lied in his confession.

The Tokyo District Court found Okada guilty in February 1997 of plotting murder for conspiring to set up a sarin plant, and of violating weapon laws for possessing a rifle.

According to the court, Okada took part in the construction of the nerve gas plant in an Aum complex at the foot of Mount Fuji between November 1993 and December 1994, and hid a rifle in a steel pillar in a cult facility.

Members of the cult stand accused of carrying out two sarin attacks -- the March 1995 attack on the Tokyo subway system that killed 12 people and injured thousands, and the June 1994 gassing in Matsumoto, Nagano Prefecture, that claimed seven lives and injured hundreds.