SEOUL, Feb 25 (Reuters) - South Korea’s central bank kept interest rates steady on Thursday, maintaining support for a fragile economic recovery while guarding against upward pressure on bond yields from the government’s fiscal stimulus package. The Bank of Korea kept the base rate steady at a historic low of 0.50%, as expected by all 27 analysts in a Reuters poll. Governor Lee Ju-yeol is due to hold a news conference from 11:20 a.m. (0220 GMT). (Reporting by Cynthia Kim, Joori Roh; Editing by Sam Holmes)