BERLIN/ANKARA (Reuters) - The German government faced an angry reaction from Turkey and accusations of hypocrisy from its own opposition on Monday after media reports that its intelligence agency spied on its NATO ally.

The reports also said the agency had listened to the phone calls of two U.S. secretaries of state - the kind of activity for which Chancellor Angela Merkel has criticized Washington.

Turkey summoned the German ambassador and called for a full explanation following a Spiegel magazine report that the BND foreign intelligence agency had been spying on Turkey for years and identified Ankara as a top surveillance target in an internal government document from 2009.

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Turkey's foreign ministry described the weekend report as "absolutely unacceptable" if true.

"It is expected that the German authorities present an official and satisfactory explanation on the claims reported by German media and end these activities immediately if the claims are true," it said in a statement.

Berlin declined to comment about surveillance on Turkey or reports in Sueddeutsche Zeitung newspaper and two broadcasters that the BND had "accidentally" overheard phone calls by U.S. Secretary of State John Kerry and his predecessor Hillary Clinton.

Last October, after reports surfaced that the United States had been monitoring her mobile phone, Merkel said that "spying among friends is not at all acceptable".

Revelations by former U.S. intelligence contractor Edward Snowden of surveillance by the United States' National Security Agency (NSA) have increased mistrust of Washington in Germany.

In an unusually public spat between the close Cold War allies, Berlin asked the top U.S. spy in Germany to leave the country in July after the Germans unearthed a double agent at the BND who admitting passing documents to American agents.

The German opposition now accuses the government of hypocrisy. Greens party co-leader Simone Peter said it was "incomprehensible" that Germany should be "actively spying on allied states" after the outcry about the NSA's activities.

Katja Kipping of the hardline Left party, itself the target of spying by the domestic intelligence agency in recent years, said the BND was "a state within the state" and needed to be brought to heel.

NO SPYING ON ALLIES?

Merkel's deputy spokeswoman Christiane Wirtz, asked about the spying reports at a news conference on Monday, declined to comment, saying intelligence activities were overseen by a government panel whose deliberations and decisions were secret.

A BND spokeswoman said on Sunday that "in principle" Germany does not carry out surveillance against friendly states like the United States and added: "Any accidental recordings are immediately erased."

But German media quoted unnamed officials saying that this stance did not necessarily apply to all members of NATO, which includes Turkey.

Asked whether Turkey was a friendly nation which should not be the target of spying, Wirtz said: "Germanycooperates closely with Turkey in many different areas".

She cited the war in Syria and insurgency in Iraq as issues of mutual interest.

Turkey's acting foreign ministry undersecretary, Erdogan Iscan, met German Ambassador Eberhard Pohl to voiceTurkey's concerns about the report. A German foreign ministry spokesman disputed media reports that the envoy had been "summoned".

Germany is Turkey's largest trading partner in the European Union and is home to some three million Turks. But relations are not always smooth and Merkel's conservatives are skeptical about Turkish EU membership.