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Comcast, the owner of NBCUniversal, is in talks to buy some of the assets of 21st Century Fox, people familiar with the discussions told NBC News on Thursday.

The sources said the talks were ongoing and in an early stage. Fox has also been having on-again-off-again conversations with Disney which was interested in buying Fox assets to bolster a direct-to-consumer internet video service.

Comcast is looking at many of the same assets that Disney was reported to be interested in, the sources said.

According to an earlier report from CNBC, the potential Disney deal would let Fox keep its news and sports channels along with the network and stations. And Fox would give up its studio and production assets and international ventures.

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Comcast is interested in Fox’s international TV distribution assets, which include a major stake in Sky, a British pay-TV company, and Star India, a pay-TV service in Asia, the sources said.

All three companies, Disney, Comcast and Fox, are already partners in the online video venture Hulu. (Time Warner also has a minority stake.)

Fox stock rose 8.46 percent in after-hours trading following a CNBC's initial report on the discussions with Comcast.

"Fox's entertainment assets represent a unique set of current and library content that is a must have in an increasingly on demand world that at some point will require a direct to consumer OTT channel," Wall Street analyst Michael Nathanson, of independent research firm, MoffettNathanson, told NBC News, referring to "Over-The-Top" media services, like Amazon Fire, Roku and Apple TV.

Related: Rupert Murdoch in talks to sell much of his media empire to Disney

The news is the latest surprise in a string of merger and acquisition talks that could shake up the ownership of America’s media giants.

Those talks have been hastened by the speed at which big technology companies are spending on content that they can monetize at a global scale. They include Netflix and Amazon, Google, Facebook and Apple. Those largely unregulated tech firms are set to spend billions on content.

Earlier on Thursday, Viacom, the owner of MTV and Comedy Central, reported flat domestic advertising revenue for the third quarter, a sign of how tough it is to eke out growth in world were viewers are migrating to ad-free services.

AT&T is also looking to merge with Time Warner but the Justice Department has said it will seek to block the merger, according to justice officials who spoke to NBC News.

Discovery Communications and Scripps Networks Interactive, owner of HGTV and Food Network, are also merging.