SINGAPORE, Nov 23 (Reuters) - Singapore"s key price gauge rose by the fastest pace in nearly three years in October, mainly driven by higher services and food inflation. The core inflation rate — the central bank"s favoured price measure - rose to 1.5% in October on a year-on-year basis, compared with 1.2% in the prior month, the Monetary Authority of Singapore (MAS) said in a statement. A Reuters poll of economists had forecast an increase of 1.3%. Singapore"s headline inflation rose 3.2%, highest since March 2013, beating economists" forecast of 2.8%. Reporting by Chen Lin; Editing by Martin Petty