Defence ministry spokesman Mohammed al-Askari said five men had been arrested after military intelligence monitored their activities for three months.
Three workshops for manufacturing the chemical agents, including sarin and mustard gas, were uncovered, he added.
Remote-controlled toy planes were also seized at the workshops.
Mr Askari said they were to have been used to release the chemical agents over the target from a "safe" distance of 1.5km (1 mile), reports the BBC's Rami Ruhayem in Baghdad.