Instagram doesn't snoop on private conversations as part of its advertising targeting strategy, the head of the popular social media site said in an interview on Tuesday.

"We don't look at your messages, we don't listen in on your microphone; doing so would be super problematic for a lot of different reasons," Instagram chief Adam Mosseri said in an interview with CBS.

"But I recognize you're not going to really believe me."

During the interview, Mosseri acknowledged that he is grilled regularly by Instagram users who insist they receive ads from restaurants, stores and other companies after only conducting a private conversation about an item and not posting to the broader site.

Like its parent company Facebook, Instagram - a social media site for posting photographs - offers a private messaging system, as well as a ­platform to post items to followers.

The issue of user privacy has been one of the many controversies dogging Facebook in the wake of revelations that defunct political consultancy Cambridge Analytica used private data from tens of millions of Facebook users for political targeting.

Mosseri said there were two ways that users may have this experience, "dumb luck" and if users are talking about a consumer good more generally.

"You saw a restaurant on Facebook or Instagram and you really like the thing. It's top of mind, maybe it's subconscious and then it bubbles up later," Mosseri said. 

"I think this kind of thing happens often in a way that's really subtle."