Erdogan, who was speaking at a meeting of an Islamic foundation in Istanbul, said the reporter, Deniz Yucel of Germany's Die Welt newspaper, would be tried by Turkey's independent judiciary.
Authorities arrested Yucel, a dual Turkish and German national, last month on charges of propaganda in support of a terrorist organisation and inciting the public to violence.
Erdogan expects parliament to restore capital punishment
He was initially detained after he reported on emails that a leftist hacker collective had purportedly obtained from the private account of Berat Albayrak, Turkey's energy minister and Erdogan's son-in-law.
He is the first German journalist to be detained in a Turkish crackdown following the failed July 15 coup that has frequently targeted the media. Berlin has said that a separate claim that Yucel was working as a German spy was "absolutely baseless".
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