The ashram of Swami Sandeepananda Giri, who supported the Supreme Court verdict allowing entry of women of menstrual age inside the Sabarimala temple, was set on fire by unidentified assailants in the early hours of Saturday, said reports.
The ashram called Swami Sandeepananda Giri's School of Bhagavad Gita is located on the outskirts of Thiruvananthapuram in Kerala.
NDTV reported that the attack took place around 2:30 am on Saturday and Maruti Suzuki Omni and a Honda CRV were also set on fire.
Kerala Chief Minister Pinarayi Vijayan condemned the incident.
NDTV quoted Vijayan as saying, "Physical attacks happen when you can't deal ideologically. We will not allow anyone to take law and order in their hands.Those who are intolerant towards Swami's activities attacked his ashram."
Vijayan is said to have visited the ashram after the incident.
Hindustan Times reported Kerala Director general of Police Loknath Behra as saying a special investigation team would investigate the attack.
Swami Sandeepananda Giri, who has been vocal about his liberal views on TV and social media, had been criticised by Ayyappa devotees for his views.
Kerala has seen massive protests in the aftermath of the Supreme Court verdict. While the temple had opened for its monthly "pooja" last week, devotees did not allow even one woman to enter the temple.
They have also approached the Supreme Court to seek a reversal of its verdict. The apex court is going to hear the pleas of the devotees on 13 November.