Former Aum Shinrikyo cult member Naoko Kikuchi pleaded not guilty on Wednesday at the Tokyo High Court in an appeal session on a five-year prison sentence.
The 43-year-old Kikuchi was convicted at the Tokyo District Court in June 2014 for her role in a 1995 parcel bombing at the Tokyo Metropolitan Government building.
She brought chemicals from the cult's facility in Yamanashi Prefecture to a facility in Tokyo in April 1995 to make explosives, according to the lower court ruling.
Other Aum members sent a parcel carrying the bomb made with the materials to the metropolitan government head offices the following month, resulting in an explosion that seriously injured a government employee, the lower court said.
It found Kikuchi guilty with assisting in attempted murder.
Kikuchi was arrested in June 2012 after 17 years on the run.
Her trial turned on whether Kikuchi knew the materials would be used to produce explosives.
The lower court found she was aware of the possibility the chemicals would be used to kill or harm people, which Kikuchi's defense counsel denied.
The court said she must have known that the cult was plotting something aimed at preventing an arrest of Aum founder Shoko Asahara, 60, whose real name is Chizuo Matsumoto.
A number of Aum members including Asahara have been found guilty in a series of crimes including a sarin gas attack on the Tokyo subway system on March 20, 1995, that killed 13 people and made more than 6,000 others ill.