"He was beaten up and water mixed with cowdung was flung on him. A probe is on," said the officer.
The person who attacked Priyanandan came forward and asked him to identify himself, the director said.
"It appears that this person was waiting for me. He came after me, hit me, poured cow dungwater on me. All this happened around 9 a.m.
"Generally I take a walk on this particular route everyday around 7 a.m., but today I got delayed. This is not a one-man attack, there are others behind this," Priayanandan said.
The 53-year-old director, whose second film "Pulijanma" received the National Award for Best Feature Film in 2006, believes the attack came due to his recent social media post on Sabarimala where the Sangh parivar forces mounted strong protests after the Supreme Court's September 28 verdict that opened the temple to women of all ages.
He had later withdrawn the post after protests on social media over his position against the Sangh parivar forces.
Condemning the attack, Chief Minister Pinarayi Vijayan said such attacks would not be tolerated as it was a direct attack on freedom of expression.
"This unholy act has taken place just because he made his point of view in the social media. Soon after his post came, he was under cyber attack. This will not be tolerated and appropriate action would be taken," said Vijayan.
Priyanandan, a known fellow-traveler of the Left, began his film career as an assistant under directors K. R. Mohanan, P.T. Kunju Muhammed.
In 2001, he directed his first feature film and till date he has seven films and numerous documentaries to his credit.