The leading social network wouldn't disclose financial aspects of the alliance with Omnicom, but online reports indicated it could be worth as much as $100 million in ads from clients the agency represents.
"Our teams are going to work hand in hand to develop and execute campaigns that provide people with amazing imagery and drive meaningful business results for advertisers."
Squires maintained that Instagram's advertising strategy will continue to involve displaying a limited number of high-quality images or videos from brands that already have a strong presence at Instagram.
Instagram in November began displaying ads as Facebook moved to start making money from the smartphone photo sharing service it bought in a billion-dollar deal in early 2012.
Instagram's opening roster of advertisers included Adidas, Lexus, PayPal, Burberry and Ben & Jerry's ice cream.
California-based Facebook is carefully adding magazine-quality photo ads to Instagram as it hopes to bring in revenue from the service without alienating users.