Nov 23 (Reuters) - British fund manager River and Mercantile Group (RIV.L) said on Tuesday it has received preliminary approaches for a possible buyout from rivals Premier Miton Group (PMIP.L) and AssetCo Plc (ASTO.L). Shares in R&M jumped as much as 11.3% to their highest in three years, while those in Premier Miton slipped 0.2% by 0859 GMT. Assetco"s stock price was unchanged. R&M has a market cap of 244.6 million pounds ($327.24 million), based on Monday"s close Any potential deal is conditional on R&M completing the planned sale of its pensions business, Solutions, R&M added. Asset managers, which actively manage funds, have been bulking up in recent years to cut costs and fight off competition from rivals running cheaper passive, or index-tracking, funds. Premier Miton"s merger interest in R&M was first reported by Sky News. R&M announced a deal last month to sell its pensions business to Schroders (SDR.L) for 230 million pounds ($316.30 million) to sharpen its focus on its primary wealth management business, which manages 3.4 billion pounds in assets. Premier Miton and AssetCo confirmed the individual approaches separately, with Premier Miton, which manages 13.9 billion pounds in assets, saying it was exploring a buyout of R&M through the issue of shares. AssetCo said it currently holds five million shares in R&M, representing about 5.85% of its voting rights. The company added that its Chairman Martin Gilbert, who is also the deputy Chairman of R&M, has recused himself from the R&M board for the purposes of talks relating to the potential bid. Gilbert formerly served as the co-CEO of blue-chip asset manager abrdn (ABDN.L). According to UK takeover rules, Premier Miton and AssetCo have to make firm offers for R&M by Dec. 21 or walk way. ($1 = 0.7476 pounds) Reporting by Aniruddha Ghosh in Bengaluru; Editing by Shailesh Kuber