Mid Day reports that the Jaan-e-mann director said he was hit by Khan late on Sunday evening.
Kunder claimed: "Shah Rukh punched and jumped on me. And he had three bodyguards with him. I don't know what got him.
"I was numb with shock so I couldn't react. He kept screaming at me, 'What do you think of yourself? I'll see to it that you're out of this industry'."
Khan was reportedly upset over negative comments surrounding Ra.One that Kunder had posted on his Twitter account.
"I was totally unprepared for this kind of an attack. If I was standing in some area where I would expect some goondaism, I would have been better prepared. But this is a classy party. Who would expect someone to jump on you from behind?" Kunder added.
The former editor's next film is the Akshay Kumar and Sonakshi Sinha 3D project Joker.
Watch the trailer for Ra.One below: