Germany's federal prosecutor's office has announced the arrest of a former domestic intelligence chief on espionage allegations.

August Hanning, who served as president of the Federal Intelligence Service (BND) from December 1998 to November 2005, was arrested on Tuesday in Bad Tölz-Wolfratshausen in southern Germany.

He is "strongly suspected of treasonous espionage, spying out state secrets, attempted treason and espionage," the federal prosecutor's office said in a statement.

A former aide, identified only as Manfred D, was arrested on the same day in Steinfurt in western Germany. He is charged with aiding and abetting attempted treason and treasonous espionage.

Manfred D had served as Hanning's chief of staff and later held the same role for several subsequent BND presidents from March 2012 until March 2026. "In his role, he had access to confidential information," the prosecutor's office said.

Prosecutors believe both men agreed, in the spring of 2010, to an arrangement in which Manfred D would continuously transmit valuable intelligence from the BND to Hanning "in exchange for remuneration."

"The current findings suggest that, over the years, Manfred D provided Hanning with approximately 2,000 documents, many of which contained classified information to be used exclusively by the federal intelligence service for internal purposes, particularly for executive intelligence briefings," the statement alleged.

Hanning is said to have used the information in his private consulting work.

On at least one occasion, prosecutors allege, he went further. "On one occasion, Hanning used classified intelligence provided by Manfred D to draft an analysis for an officer of a foreign intelligence service," the prosecutor's office said.

The office did not identify which country the foreign officer worked for and added: "It has yet to be determined if the material reached the intended recipient."

The prosecutor's office did not reveal which foreign power, if any, the men are ultimately suspected of spying for.

The premises of both men were searched on Tuesday.