STOCKHOLM, Nov 23 (Reuters) - Specialty pharma group Karo Pharma (KARO.ST) has agreed to buy Belgium-based Sylphar International from Vendis Capital and Sylphar"s founder for 290 million euros ($326 million), it said on Tuesday. Karo Pharma said Sylphar, which develops and markets over-the-counter products, would boost its market position and help it grow, particularly in the digital marketplace. The Swedish company added that it would carry out a new share issue of around 200 million to 250 million euros, with preferential rights for its existing shareholders. Karo Intressenter AB, owned by private equity firm EQT (EQTAB.ST) and which has a 79.85% stake in Karo Pharma, is supporting the transaction, it said. "Karo estimates that the transaction brings synergy potential for the company, predominantly in the form of sales synergies," Karo Pharma said in a statement. Sylphar, whose main brands are Nutravita, Alpha Foods and Remescar, had sales of around 64 million euros in the October-September period. Karo Pharma said an additional payment of 10 million euros may be paid if certain growth targets for Sylphar are met, adding the transaction would be completed in January 2022. ($1 = 0.8901 euros) Reporting by Helena Soderpalm; editing by Niklas Pollard