Nokia is to pay $8.1 billion (£4 billion) for Navteq, an American digital map supplier, in an attempt to develop new revenue streams and to defend its No 1 position in the mobile phone market against internet groups such as Google.

The acquisition marks the group’s largest takeover and its latest effort to expand beyond its core business, but analysts balked at the $78-a-share cash offer and shares in the Helsinki-listed group fell as much as 4 per cent, recovering to close down 2 per cent at €26.17.

Navigation is one of the hottest segments in the technology industry, with sales of personal mapping devices expected to triple in the next four years.

Richard Windsor, a Nomura analyst, said: “This is an expensive, defensive move.”

He added that the deal was partly about enabling Nokia to “keep one step ahead of companies such as Google, Yahoo! and Apple, who are all trying to get a piece of the mobile content and services market”.

Nokia faces growing margin pressure in its core business. Google, angling for a slice of the potential $11 billion mobile advertising market, is understood to be developing a handset, and Apple has forged into the mobile sector with its iPhone.