German press reports suggest the country's intelligence agency spied on Turkey for years.
Turkey has summoned Germany's ambassador over the allegations.
Der Spiegel magazine said Berlin had identified Ankara as a top surveillance target, citing a 2009 government document.
Turkey's foreign minister Ahmet Davutoglu said: "If these claims are true, the German authorities must give an official and satisfactory explanation on the reports in the German media and end these activities immediately."
German Chancellor Angela Merkel is no stranger to spying. She was furious when she found out her mobile phone had been tapped by the US National Security Agency.
"It is the case that I don't publicise the details of the work of the German [intelligence] agencies," Merkel said in a statement.
"What is necessary will be said and discussed in the parliamentary supervisory committee [PKGR] and there, as far as it is necessary, the parliamentary body will be given what further information they need," she added.
After her mobile phone scandal,Merkel famously said, "spying among friends is not at all acceptable."
Turkey's largest trading partner in the EU is NATO ally Germany.
Source: Euronews
Photo Source: The New York Times
