WikiLeaks has released details of the US National Security Agency (NSA) spying on German Chancellor Angela Merkel.

The NSA apparently tapped Merkel’s phone calls for years, with WikiLeaks claiming that the spy agency also kept an eye on her closest advisers along with the staff of her predecessors.

Some of the targets included Merkel’s former chief of staff Ronald Pofalla, former chancellor Gerhard Schroeder (in office 1998-2002), and former Chancellor Helmut Kohl.

The NSA reportedly placed long-term surveillance on 125 phones belonging to top German officials.

WikiLeaks published three NSA intercepts of Merkel’s conversations and the data included Merkel’s telephone numbers, her aides, her office and her fax machine.

The website also released intercepts that contained information regarding an international financial crisis in 2009, and the conversation Merkel had with the prince of the United Arab Emirates in 2009 on Iran.

WikiLeaks editor-in-chief Julian Assange said: "There is now proof enough of NSA surveillance on German soil. It is time to reopen the investigation and for the NSA to stop engaging in its illegal activities against Germany."

The news comes just after US President Barack Obama said that US and Germany were "inseparable allies" in order to put the spying allegations behind them.