Murdoch's Twenty-First Century Fox had offered 18.5 billion pounds ($25.8 billion at the current exchange rate) in December 2016 for the 61 percent of Sky it did not own. However, U.S. cable television giant Comcast announced Tuesday it would challenge the bid with an offer worth around 22 billion pounds ($31 billion).
"I think it is apparent right now that we are going to see a bidding war for Sky," Paolo Pescatore, vice president of multiplay and media at CCS Insight, told CNBC, which is owned by Comcast.
Alex De Groote, digital and media analyst at Cenkos Securities, agreed, saying Comcast's "opportunistic" bid would likely spark a "fully-blown auction."
Laith Khalaf, senior analyst at Hargreaves Lansdown, said Comcast had effectively "gazumped" Fox with a better takeover offer for Sky shareholders.
Khalaf added it remains to be seen whether Murdoch's Fox has the appetite to try to counter Comcast's offer. This is perhaps especially relevant given the fact Fox has agreed to sell a string of its assets, including Sky, to Disney.
"This isn't a done deal yet though," Khalaf added. "The market clearly smells the scent of some more action before this saga draws to a close."
Comcast said it had not engaged with Sky ahead of its possible takeover bid and a spokesperson for Sky declined to comment. Disney CEO Bob Iger also declined to make any comment, according to Reuters.
"At this point we have to remember that it is not really Fox, it's Disney," said Brett Harris, research analyst at Gabelli. "So it's really what does Disney want to do. ... For the same reason that Comcast wants Sky, I think Disney wants Sky."
Comcast's offer for Sky comes at a time when traditional cable television networks have been losing customers to streaming services such as Amazon and Netflix.
When asked whether Comcast's move to buy Sky could prompt other media companies to consider takeover bids in Europe, CSS Insight's Pescatore replied: "For sure. We are going to see huge disruption ahead, and that's very much driven by the online giants such as Amazon and Netflix."
The offer pits the biggest cable operator in the U.S. against Fox. However, Disney has also agreed to buy a string of assets from Fox — including its current 39 percent share of Sky — making the picture more complicated.
Comcast, which owns NBC and Universal Pictures, said it was offering 12.50 pounds per share. That is significantly higher than the 10.75 pounds per share agreed by Fox.
In a conference call with investors Tuesday, Comcast Chairman and CEO Brian L. Roberts said a Comcast-Sky deal would be a "perfect fit," and that he was confident it would be able to receive the necessary regulatory approvals in a "timely manner."
Earlier this month, Sky won a bulk of Premier League soccer television rights for the seasons between 2019 and 2022. This renewed calls from Sky investors to urge Fox to improve its offer in order to keep its takeover plans on track.
Similarly, Fox investors have also reportedly claimed Disney should be paying more.
Murdoch's takeover bid has repeatedly been held up by regulatory concerns and, last month, the U.K.'s competition authority provisionally found Fox's bid for Sky would not be in the public interest, citing concerns that the Murdoch Family Trust would have too much influence over public opinion and the political agenda.