Facebook Inc Chief Executive Mark Zuckerberg stumbled at a congressional hearing on alleged abuse of market power on Wednesday, as lawmakers confronted the social media titan with damaging internal emails about the company's acquisitions.

Using the exchanges, lawmakers got Zuckerberg to acknowledge that he saw photo-sharing app Instagram and messaging app WhatsApp as competitors when Facebook acquired them.
 

"The businesses are nascent but...if they grow to a large scale they could be very disruptive to us," Zuckerberg wrote in 2012, two months before the Instagram purchase.

In another email, written the same day Facebook announced the acquisition, Zuckerberg conceded that "Instagram was our threat," adding: "one thing about startups though is you can often acquire them."

Representative Joe Neguse, a Democrat, noted that a 2014 email showed Facebook's CFO referring to the company's acquisition strategy as a "land grab."

"We have name for this; it is monopoly," Neguse said.

The committee presented fewer such exchanges to the other executives testifying at the hearing, which also featured Amazon.com Inc's Jeff Bezos, Alphabet Inc-owned Google's Sundar Pichai and Apple Inc's Tim Cook.

Democratic Representative Pramila Jayapal used an email to grill Zuckerberg on whether Facebook copied competitors like Snapchat for anti-competitive reasons.
 

"How many competitors did Facebook end up copying?" she asked. "I don't know," Zuckerberg answered, stammering.

She asked if Facebook had ever threatened to clone a competitor's feature while negotiating to buy them. "I would like to just remind you that you are under oath and there are quotes from Facebook's own documents," she told him.

The documents also shed new light on how the social media giant saw the competitive landscape. In a 2012 graphic, Facebook touted the company as "95% of all social media in the U.S." The graphic was titled: "The industry consolidates as it matures."