BERLIN—German police carried out a nationwide crackdown Wednesday on racist and xenophobic postings on the internet and social media that they say have surged since last year’s large influx of refugees into the country.

In raids coordinated by the federal criminal police agency BKA, police across 14 states raided the homes of 60 people suspected of being behind the postings, which are illegal under German law. No arrests were made, the agency said.

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