BEIJING—A Chinese court sentenced a former senior intelligence official to life in prison for corruption, after convicting him of taking millions of dollars in bribes from a businessman-turned-critic of the ruling Communist Party.

Thursday’s verdict against Ma Jian, a former vice minister of state security, extends a long-running government campaign to discredit the exiled tycoon, Guo Wengui, and his claims about corruption in the party’s highest echelons.

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