He also asked the state governments to take stringent action against them.
Modi, while addressing a public meeting after inaugurating a host of development projects here, accused the cow vigilantes of trying to create tension in the society and said they should be exposed and punished.
"I want to tell everybody beware of these fake cow protectors. These handful of vigilantes have nothing to do with cow protection, but want to create 'tanaav' (tension) in the society," Modi said.
Describing cattle as country's wealth and not burden, the Prime Minister made a mention of a Himachal Pradesh Governor's campaign of protecting abandoned cows and handing them over to farmers to use them for agricultural activity.
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"Cow will never become a burden. Cow urine and dung are used in agriculture," he said, adding that cow should be linked to the country's economic development.
"But fake (cow protectors) destroy society and country. We need to beware of these people. There is a need to punish these people. Then alone can we take the nation to great heights," the Prime Minister said after inaugurating a host of development projects.
Modi's comments come at a time when his government and BJP are facing flak over incidents of violence against Dalits and Muslims by cow vigilantes in various states including Uttar Pradesh, Gujarat and Madhya Pradesh.
Modi unveiled a plaque in Medak district's Komatibanda village in Gajwel constituency, represented in the Assembly by Telangana Chief Minister K Chandrasekhar Rao, and formally turned on a water tap on the premises to mark the occasion.
This is Prime Minister's maiden visit to Telangana after formation of the state in June 2014.
Modi unveiled plaques to mark the laying of the foundation stone for the 152-km Manoharabad-Kothapalli new railway line (connecting Hyderabad and Karimnagar), NTPC's Telangana Super Thermal Power Project Stage-1 (2x800 MW), Ramagundam, Kaloji Narayana Rao University of Health Sciences, Warangal and revival of Ramagundam fertiliser plant (Karimnagar district).
Governor of Telangana and Andhra Pradesh E S L Narasimhan, Chief Minister K Chandrasekhar Rao, Union Ministers M Venkaiah Naidu, H N Ananth Kumar, Suresh Prabhu, Piyush Goyal and Bandaru Dattatreya were among those present.