The National Security Agency (NSA) has reportedly been spying on German Chancellor Angela Merkel and other high-ranking officials from other nations. The leaked data prompted Merkel to confront U.S. President Obama over the phone.

Sources said the German Chancellor called Obama Wednesday saying that the activity was a "breach of trust." Obama reportedly told Merkel that he was unaware of it.

The NSA 'spying' allegedly started in 2002 according to sources and the U.S. has been listening to Merkel's mobile phone conversations since then.

The German press reported Sunday that German authorities are now studying what legal case to file the United Nations against the espionage scandal.

NSA's Chief Keith Alexander briefed U.S. President Obama about the operation but the president reportedly "did not halt" it.

Der Spiegel wrote that leaked documents from the NSA showed the German Chancellor's phone as one of the spying targets of the U.S. Government. According to sources, Merkel was still under U.S. surveillance during Obama's June visit to Berlin.

In another report by Der Spiegel, Merkel was believed "outraged" by the information.

India Times reported that the German Government will be sending its intelligence chief to Washington to get answers from the American Government. The espionage scandal also prompted Berlin to talk to the U.S. ambassador.

Protesters gathered in Washington Saturday to call for the government's curbing of NSA activities.

Dubbed as the most powerful woman in Europe, Merkel was 'spied on' by the NSA and even stepped up its efforts by listening in to two phones. According to India Times, U.S. intelligence was able to hear her conversations and read her text messages to key officials.

Merkel's predecessor Gerhard Schroder was also in NSA's sights during his term due to his opposition against the Iraq war and his closeness to Vladimir Putin.

Hans-Peter Friedrich, the German Interior Minister said, "Surveillance is a crime and those responsible must be brought to justice."

Sources noted the Germans were "appalled" by this action of the Americans and reportedly want the Americans to apologize.