It also demanded that those involved in the violent attack on the daily's press and its employees should be brought to book and punished under law.
Mathrubhumi newspaper's Kottakkal unit was attacked on May 31 by a group of people protesting against a road accident. The staff present in the office were injured and furniture damaged in the attack.
"The Executive Committee of the INS, which met today at New Delhi, strongly condemned the attack against Mathrubhumi, a respected media organisation in Kerala.
The leading organisation of newspaper publishers said the attack was an act of cowardice adding such unjustifiable incidents posed a great threat to democracy.