Germany has launched an investigation into what is believed to be the activities of a suspected mole in its military, with reports suggesting the individual is a U.S. spy. It comes just days after the European power arrested a member of its foreign intelligence over claims that he was a double agent for America.

Federal prosecutors in Germany said Wednesday that police had raided properties in the Berlin area on "initial suspicion of activity for an intelligence agency." They did not elaborate or specify what intelligence agency was involved but said they had not made an arrest.

But the suspect is "from the military," a security source told Reuters, speaking on condition of anonymity. The daily Sueddeutsche Zeitung also reported, without naming sources, that the man being investigated worked in "the military field" and is suspected of spying for the United States.

If confirmed, the latest allegations could further harm Berlin’s relations with Washington, which have already been strained by espionage accusations.

The latest investigation comes just days after Germany arrested a 31-year-old employee of the BND foreign intelligence service who admitted he passed documents to a U.S. contact. German media have reported he also offered his services to Russia.

U.S. Ambassador to Germany John B. Emerson was at the Foreign Ministry for the second time in five days on Wednesday for a meeting with a senior official, said a German official who spoke on condition of anonymity because he wasn't authorized to discuss the case publicly. It wasn't immediately clear whether Emerson was summoned and whether the discussion involved the new case.

German Chancellor Angela Merkel said Monday that if it proved to be true that the BND officer was spying for NATO ally the United States, it would be a "serious case."

The documents passed on by the BND foreign intelligence official include details of a parliamentary committee's investigation of former U.S. intelligence contractor Edward Snowden's allegations that Washington carried out surveillance in Germany, including of Merkel's telephone.

The new case is believed to be more serious than last week's, Sueddeutsche Zeitung daily said in an advance copy of Thursday's edition.

The Defense Ministry confirmed that an investigation was going ahead but declined to give any further details. The U.S. Embassy in Berlin was unable to comment.

Merkel said Wednesday that there were talks with the United States, but she could not comment on their content.

Two U.S. officials familiar with the case of the arrested BND official told Reuters on Monday the CIA was involved in a spying operation against Germany that led to the alleged recruitment of a German intelligence official.

Surveillance is a sensitive issue in a country where the memory of the Nazis' Gestapo secret police and communist East Germany's Stasi means the right to privacy is treasured.

After the Snowden revelations, Berlin demanded that Washington agree to a "no-spy agreement," but the United States has been unwilling to make such a commitment. German officials also emphasize that they rely on intelligence from U.S. agencies.

Wire services