OSLO ( TheStreet) -- A group of investors are attempting to derail Cisco's ( CSCO) acquisition of Tandberg, prompting speculation that Cisco may have to increase its $3 billion bid for the Norwegian video-conferencing specialist.

Holders of 24% of Tandberg's stock do not intend to tender their shares, according to the Financial Times, but are open to a higher offer from Cisco or another company.

The FT reports that shareholders including the Oslo Pension Fund and Rasmussen Group are resisting Cisco's overtures, citing Tandberg's ability to generate strong revenue as an independent company.

Cisco announced the deal on Oct. 1, paying an 11% premium on the previous day's closing price for Tandberg's stock. This, however, was well below the 20% premium it is paying for Starent Networks ( STAR) in a $2.9 billion deal announced earlier this week. Back in 2007, Cisco paid a 23% premium for WebEx, a $3.2 billion acquisition which laid the foundations for its video conferencing push.

Norwegian brokerage SEB Enskilda, which represents the 21 activist shareholders, highlighted Tandberg's ability to thrive in a growth market. "Videoconferencing is a big field," said Peder Strand, SEB Enskilda analyst, according to the FT. "It is moving out of the traditional meeting room and onto the corporate desktop -- we are very positive on the company and the shares."

"We are aware of statements made by Tandberg shareholders and as we are currently in the middle of a tender offer process, we are not able to comment," explained a Cisco spokeswoman, in an email to TheStreet. "We have stated previously that we believe we are paying a fair price for a quality asset and our offer comes recommended by the Tandberg board of directors."

The spokeswoman also pointed to Tandberg communications with the Oslo Exchange which said that Cisco's offer represents a 38.3% premium to the closing share price on Jul. 15., one day prior to major media reports of a possible acquisition.

Cisco CEO John Chambers has been making a song and dance about video for years, although his firm's efforts argely centered on the high end of the market. Tandberg would extend this reach downstream. The Norwegian firm recorded sales of $808 million last year and is seen as the 800-pound gorilla in video conferencing.

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