A spokesman for the Federal Prosecutors Office says the suspects are believed to have "spied on institutions and persons in Germany on behalf of an entity associated with Iran."
Weekly news magazine Focus said the raids were mounted in the nation's capital Berlin as well as the states of Baden-Wuerttemberg, North Rhine Westphalia and Bavaria.
The spokesman, Stefan Biehl, told The Associated Press that Tuesday's raids were prompted by a tip from Germany's domestic intelligence service.
He declined to comment on a report that the suspects were spying on Israelis in Germany.
Germany said two weeks ago it had summoned Iran's ambassador to reprimand Tehran against spying on individuals and groups with close ties to Israel, calling such acts a completely unacceptable breach of German law.
The move comes after the March conviction of a Pakistani man for spying for Iran in Germany went into force.
Mustufa Haidar Syed-Naqfi was convicted of gathering intelligence on Reinhold Robbe, the former head of the German-Israel Friendship Society, and an Israeli-French economics professor in Paris, for Iran's elite Revolutionary Guards.
The Foreign Ministry summoned the Iranian ambassador to deliver the unusually sharp rebuke once the German constitutional court rejected his appeal. The meeting took place on Dec. 22 but was not disclosed until now.
"Spying on people and institutions with special ties to the state of Israel on German soil is an egregious violation of German law," a ministry official said.
The official said Philipp Ackermann, acting director of the Foreign Ministry's political section, had told the Iranian ambassador that "such activities would not be tolerated and were completely unacceptable".
Germany has played a key role in European efforts to persuade Washington to keep the nuclear accord in place, an issue that will come up again late this week, when U.S. President Donald Trump must decide whenter to reimpose oil sanctions lifted under the agreement.
Germany's domestic intelligence service, which handles counterespionage, highlighted Iran's spying activities in its annual report in July, noting that Tehran was focused heavily on Israeli or pro-Jewish targets.
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