While convict Abdul Aziz was awarded seven years jail term, the rest 20 were sentenced to five years imprisonment each by NIA Special Judge S Santhosh Kumar.
The court, which found them guilty under various sections of IPC, Unlawful Activities Prevention Act (UAPA, Arms Act and Explosives Act, also imposed a fine of Rs 5000 each on the convicts.
In default, they will have to undergo jail term for six months more.
Arguing for maximum punishment to the guilty, NIA prosecutor P G Manu cited a Kerala High Court ruling in a terror case which said "sympathy has no role in dealing with terrorist case".
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Though the counsel for the accused pleaded that there was no casualty in the case, the judge said, "There is no casualty because of the action of police."
On April 23, 2013, a police team had raided a house in a coconut farm in Narath and seized arms and ammunition and 21 mobile phones.
The state government had handed over the case to NIA.
Police had suspected that the arrested people had connections with some extremist organisations, including Indian Mujahideen.