Takeover speculation surrounding UK-based drugs giant AstraZeneca has pushed up its stock market valuation by more than £4bn.
The group declined to comment on weekend reports that larger US rival Pfizer had made a tentative approach that could possibly value it at more than £60bn.
Analysts expressed scepticism about the possible deal with experts at Deutsche Bank saying it would require a "leap of faith" in AstraZeneca's new drugs pipeline.
But shares were almost 10% higher at one point, adding £4.6bn to its worth, though this later settled back to around 7%.
Senior investment bankers and industry sources told the Sunday Times that informal conversations about a possible tie-up had taken place in recent weeks.
Astra was reportedly resisting the advances, with no talks currently under way, but it was said that Viagra maker Pfizer could come back with a fresh approach – a move that would mark the biggest-ever foreign takeover of a UK business.
AstraZeneca, which employs more than 50,000 people around the world including 6,700 in the UK, will be under pressure to shed light on any discussions when it publishes first quarter financial results on Thursday.
Unions and MPs have voiced concerns about the potential impact on jobs and manufacturing exports from any takeover deal.
What AstraZeneca could be worth should rival Pfizer launch a takeover