"Mere possession of certain kinds of literature cannot be a ground for arresting someone", said Shemeer Babu, Programmes Director, Amnesty International India.
"Authorities must respect the right to freedom of expression, which includes the right to seek and receive information of all kinds", he said in a statement.
On Jan 30, police had arrested Jaison C Cooper, a human rights activist, and Thushar Nirmal Sarathy, a lawyer, in Kochi and Kozhikode respectively.
The release also mentioned the arrest of two college students from Palakaad on Dec 22 last year under the act for allegedly attacking two fast food outlets the previous day.
In recent weeks, the Kerala police have detained several people across the state on suspicion of being supporters of banned Maoist armed groups. Some have been subsequently released, it said.