A 62-year-old retired Navy officer was beaten up allegedly by Shiv Sena activists after he forwarded a cartoon on Maharashtra Chief Minister Uddhav Thackeray on WhatsApp on Friday, the police said.
Four men were arrested in connection with the incident, they said.
The incident took place around 11.30 am in Lokhandwala Complex area in suburban Kandivali, an official said.
"Retired Navy officer Madan Sharma had forwarded a cartoon on Thackeray on a WhatsApp group. Some Sena workers went to his house and beat him up. Sharma sustained an eye injury and is being treated at hospital," he said.
A case under IPC section 325 (causing grievous hurt) and provisions related to rioting was registered against six persons.
Meanwhile, the Navy veteran's daughter Sheela Sharma has demanded President's rule in Maharashtra, saying there is "no humanity left" in the state.
"My father received threats for forwarding a message. A number of people from Shiv Sena attacked him. Later, police came to our residence & insisted on taking my father with them. We've registered FIR," she added.
Opposition leader Devendra Fadnavis expressed shock and appealed to the Chief Minister to take action against the accused.
"An extremely sad and shocking incident. A retired naval officer got beaten up by goons because of just a Whatsapp forward. Please stop this GundaRaj Hon Uddhav Thackeray ji. We demand strong action and punishment to these goons," Fadnavis tweeted, along with a picture of the officer.