The U.S. embassy, center, is pictured next to the Brandenburg Gate and the Holocaust Memorial, right, in Berlin October 27, 2013. (Fabrizio Bensch/Reuters)

German Interior Minister Hans-Peter Friedrich said Sunday that U.S. intelligence agencies broke German laws if they monitored cellphones in Germany, following a new report that the United States may have been monitoring Chancellor Angela Merkel’s phone since 2002.

Merkel’s communications may have been tapped even before she became leader of Germany in 2005, according to the German newsmagazine Der Spiegel, citing a leaked National Security Agency document from former contractor Edward Snowden. Eavesdropping activities were run out of the U.S. Embassy in Berlin as well as in about 80 other embassies and consulates around the world, including 19 in Europe, the magazine reported, citing another document leaked by Snowden.

If it were disclosed that diplomatic facilities were being used to do spying, “serious harm” could be done to relations with host countries, Der Spiegel reported one document said. But the magazine said that it was not clear from the leaked documents whether intelligence agencies had been listening to Merkel’s conversations or whether they had simply been collecting connection data.

The allegations over spying have created an uproar in Europe, especially in Germany, where furious officials have said that they felt U.S. spy agencies had treated them not as being among America’s staunchest allies but as though they were untrustworthy enemies. Merkel said last week that she would press for clear guidelines about what U.S. intelligence agencies were permitted to do on German soil.

Friedrich, the interior minister, was quoted on Sunday as saying that he wanted legal consequences if crimes had been committed.

German Chancellor Angela Merkel attends a meeting during the European Union Summit of Heads of States held at the European Union Council building in Brussels on October 25, 2013. (YVES HERMAN/AFP/Getty Images)

“If the Americans eavesdropped on cellphones in Germany, they broke German law on German soil,” Friedrich, the interior minister, was quoted as saying on Sunday by the Bild am Sonntag newspaper. “Eavesdropping is a crime and those responsible must be held accountable,” he said.

German news reports on Sunday offered contrasting accounts of when President Obama might have known of any spying. In a Wednesday conversation between Obama and Merkel, he told her that he had not known that her cellphone had been monitored, the German newspaper Frankfurter Allgemeine Sonntagszeitung reported on Sunday, without citing its source. But the Bild am Sonntag newspaper, citing an unnamed NSA official, reported Sunday that NSA chief Keith Alexander had informed Obama of the monitoring in 2010.

U.S. spy agencies sometimes use “false architectural features or roof maintenance sheds” on diplomatic outposts to hide antennas used for intelligence-gathering, according to one NSA document published Sunday by Der Spiegel. On its cover, the magazine printed a photograph of the U.S. Embassy in Berlin, circling the roof shed that it said it believes contains monitoring equipment. The Berlin embassy is unusually central for an American diplomatic seat in this security-conscious era, 300 yards away from the German parliament and within sight of the chancellery where Merkel works.

The teams that do the monitoring are small, the document said, and “their true mission is not known by the majority of the diplomatic staff at the facility where they are assigned.”

The disclosure that Merkel’s cellphone may have been monitored since 2002 — the year she became the leader of the opposition in parliament — raised questions about whether other top German leaders had also been monitored, German officials said Sunday.

The dispute continues to threaten discussions about a U.S.-E.U. trade agreement. Merkel is working to form a new coalition with the center-left Social Democratic party, whose leaders have called for putting the trade talks on hold until they receive answers from the United States about the spying allegations.