Brewing giants Carlsberg and Heineken have said that they are in talks about forming a consortium to buy Scottish & Newcastle (S&N).
They said there was no guarantee an offer would be made for the firm, whose brands include Foster's, Kronenbourg 1664 and Newcastle Brown Ale.
S&N said any forthcoming bid would be "unwelcome" and that it was committed to being an independent firm.
Edinburgh-based S&N is the largest UK-owned brewing company.
"S&N is confident in its future as an independent group with a combination of strong growth in emerging markets and cash generation in developed markets," it said.
"S&N strongly urges shareholders to take no action at this time."
If Denmark's Carlsberg and Holland's Heineken do go ahead and make a bid, their plan is to split S&N between them.
Heineken would take control of S&N's main business in the UK, and some other European markets.
While Carlsberg would take over S&N's operations in France and Greece.
Carlsberg would also gain full control of Russia-based brewer Baltic Beverages Holdings, which is currently jointly owned by it and S&N.
S&N has long been seen as a possible takeover target, and its shares closed up nearly 19% at 756p on news of the bid approach.
Newcastle Brown Ale
Carlsberg and Heineken had both been named as potential individual bidders in the past.
Diageo and SABMiller are other drinks firms which have been linked with a possible takeover.
Earlier this year, Carlsberg restructured, giving it more scope to raise capital and therefore take part in merger or takeover activity.
Last month, S&N's chief executive Tony Froggatt said that he was calling time on his career at Britain's biggest brewer.
He will be succeeded next month by John Dunsmore, currently head of the company's UK and European brewing operations.
One analyst said he believed Scottish & Newcastle investors would not be willing to sell for anything less than 750p a share.
"It is early days, but clearly Scottish & Newcastle is in play and the market is reacting very strongly to this," said Clem Chambers, from investor website ADVFN.com.
Fellow analyst Richard Withagen of SNS Securities said a joint Heineken-Carlsberg takeover of S&N would make good sense.
"I think from a strategic point of view, it's obviously a good deal for Heineken and Carlsberg," said Mr Withagen.
"Heineken would gain market leadership in the UK and become the number two in Belgium and Portugal and a leading market player in Finland."
S&N was the world's seventh largest brewer in 2006 in terms of total sales volumes. Heineken and Carlsberg were ranked fourth and fifth respectively.