BEIJING — In his first speech to the Chinese Communist Party’s elite Politburo, Xi Jinping, the new party chief, denounced the prevalence of corruption and said officials must guard against its spread or it would ‘‘doom the party and the state.’’

The remarks were made Saturday at a meeting of the 25-person Politburo, which announced a turnover of 15 members last week at the close of the 18th Party Congress, the state news media reported Monday.