PARIS—As many as 300 graves were desecrated at a Jewish cemetery in eastern France, officials said Sunday, the latest escalation in a wave of anti-Semitic violence in Europe.

French officials are searching for an unknown number of assailants who upended or broke tombstones and headstones in roughly three quarters of the 400 graves at a historic Jewish cemetery in Sarre-Union, a small town near France’s border with Germany, a person familiar with the inquiry said.

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