DALLAS (REUTERS) - Facebook Inc Chief Executive Officer Mark Zuckerberg took the witness stand in Dallas federal court on Tuesday (Jan 17) and denied an allegation by a rival company that Facebook's virtual-reality technology of its Oculus unit was stolen.

Zuckerberg, wearing a suit and tie rather than his typical T-shirt, was still on the witness stand after more than an hour of testimony in a civil lawsuit brought by videogame publisher ZeniMax Media Inc.

ZeniMax sued Oculus in 2014 as Facebook was in the process of buying the startup for US$2 billion over allegations that Oculus unlawfully gained access to ZeniMax's intellectual property.

Zuckerberg told the jury: "I'm here because I believe they're false, and it's important to testify to that."

He added: "Oculus products are based on Oculus technology."