RSS chief KS Sudarshan on Monday suggested conversion and demographic change in parts of India posed an "invisible threat" to Hindu society.
There is "an invisible and silent attack being waged against the community to weaken it from inside", he said adding, "We have to remain vigilant against such attempts".
Sudarshan was releasing a book written by Janata Party leader Subramanian Swamy in New Delhi.
He said that after the wave of foreign invasions right from Mughals to the British the country was "losing its focus and identity".
"Hindus should awaken and search for their identity to defeat evil forces who are trying to destroy their culture," he said and asked everyone to raise their voice against religious conversion.