Japanese advertising company Dentsu snapped up British-based media group Aegis for £3.16 billion ($4.89 billion, 4.0 billion euros) on Thursday, sending Aegis shares rocketing.
The surprise deal will create a new global player to compete against the likes of advertising titans Omnicom, Publicis and WPP.
"The boards of Dentsu Inc. and Aegis Group plc are pleased to announce that they have reached agreement on the terms of a recommended cash offer pursuant to which Dentsu will acquire the entire issued and to be issued ordinary share capital of Aegis," the firms said in a statement to the London Stock Exchange.
The offer, pitched at 240 pence per share, represents a premium of 48 percent from Wednesday's closing share price level.
In reaction, Aegis shares surged 45.6 percent to 236.2 pence in late morning deals on Thursday, as investors welcomed the bid. London's second-tier FTSE 250 index, on which Aegis is listed, was down 0.68 percent.
"The combination of Dentsu and Aegis will create a new global communications network for the digital age focused on delivering best-in-class brand, media, digital and marketing services for the combined client base through a fully-integrated and scalable platform," the statement said.
It added that the new company will "combine Dentsu's leadership position in the Asia-Pacific region and rapidly growing presence outside Asia with Aegis's leading position in Europe, strong footprint in Asia and Australia and its market leading growth in North America and the faster-growing regions".
Dentsu said it has already bought or had undertakings for about 30 percent of Aegis shares, mainly from French businessman Vincent Bollore.
Bollore, the group's biggest shareholder, will receive approximately £535 million for his 15-percent holding.
"Dentsu and Aegis will be the market leader in the Asia-Pacific region, enjoying a strong presence across Europe and the fastest growing agency network in the United States," said Dentsu President and Chief Executive Tadashi Ishii.
"We have huge ambitions for a truly client-focused global communication network built in the digital age."
Aegis chief executive Jerry Buhlmann described the deal as "compelling".
"This is a compelling combination of two great businesses that will create one of the world's most dynamic marketing services groups -- and the first to be born in the digital age," he said.
"We at Aegis are delighted at the prospect of being able to play a full part in helping Dentsu create a platform for global growth and continued digital innovation."
Aegis had previously been a takeover target for French marketing group Havas, in which Bollore is the biggest investor.