In a statement released today, the National Security Service says Vahan Aroyan was arrested at his home in the western Armenian village of Lusatar.
The statement says security officials found a large weapons cache, including grenade launchers and surface-to-air missiles.
Authorities claim Aroyan has ties with two opposition activists from the Association of Armenian Volunteers who face charges of plotting a coup against the government.
But Armen Yeghian, a senior member of the Association of Armenian Volunteers, told RFE/RL's Armenian Service that Aroyan is not linked to the group.
"He and his activities have no practical connection with our structures," Yeghian said.
The group has denounced Aroyan's arrest as part of a state campaign against dissidents.
(with material from AP)