Thushara Peiris was set upon by a furious mob outside Gemini Studios in Chennai, capital of southern Tamil Nadu state, on Monday, witnesses said.
He was rescued by film studio staff and police, and flown back to Colombo -- but has lost the original film rolls which are still with the studio.
"They punched me on the eye, on the nose and hit me on my head. I fell on the ground," Peiris, 39, told AFP from his bed in a hospital in Sri Lanka late last week.
"I was ultimately rescued and returned to Colombo the same evening. I want the studio to return my film and the negative without damage," he said.
Sri Lanka's foreign minister Rohitha Bogollagama, meanwhile, promised to use diplomatic channels to secure the release of the film footage, a state-run Sri Lankan newspaper reported on Saturday.
Sri Lanka's Tamil Tiger rebels still command some support in Tamil-majority parts of India, even though they are held responsible for the 1991 murder of former Indian premier Rajiv Gandhi and bra