A German intelligence officer has reportedly been arrested over a suspected Islamist plot to bomb the agency's headquarters in Cologne.

The 51-year-old official was said to have made a "partial confession" to the plot, according to Der Spiegel.

The suspect attempted to pass on "sensitive information about the BfV (Germany's domestic security agency), which could lead to a threat to the office", an official told the newspaper.

"He is accused of making Islamist remarks online under a false name, and offering internal information during chats," a BfV spokesman said.