Getty ImagesGerman security officials say they are carefully examining possible indications of foreign finance or influence in a series of attacks in German cities in the past year.
However, they have reacted coolly to a German TV report suggesting suspicious internet searches were carried out in Russia before a deadly attack in Mannheim last year.
A 26-year-old Afghan man has admitted a knife attack that targeted anti-Islam activist Michael Stürzenberger and killed a police officer in May last year, days before European elections.
A ZDF TV report has now suggested that Russian Google searches days earlier had included "terror attack in Mannheim" and "Michael Stürzenberger stabbed".
Digital intelligence analyst Steven Broschart told the public broadcaster ZDF's Terra X History programme that the searches were highly unusual: "it's pretty unlikely that we're talking about a coincidence here".
He spoke of Russian internet searches for webcams in Mannheim's market square before the 31 May attack took place.
The broadcaster also highlighted fires inside parcels at a DHL cargo hub in Leipzig which Western security officials blamed on Russia's GRU military intelligence agency.
That attack in August 2024 preceded regional elections in Saxony, and the head of domestic intelligence Stephan Joachim Kramer in neighbouring Thuringia told ZDF that "those who deal with this know we've actually been at war for a long time, even if it's not been declared".
The trial of the man accused of carrying out the Mannheim attack, Sulaiman A, has heard how he became fascinated by jihadist group Islamic State and how he had ordered a knife online beforehand.
Other German cities have since been hit by attacks, including this year in Aschaffenburg and Munich, ahead of federal elections. The killings coincided with a spike in support for the far-right anti-immigration party, Alternative for Germany.
Interior ministry officials have not commented on ZDF's report on Russian internet searches four days before the Mannheim attack, other than to say the issue of "possible indications of targeted influence from abroad" was being taken seriously.
There were "no clear indications" so far, the spokesman told AFP news agency.
Meanwhile, a spokesman for Germany's BND intelligence service voiced scepticism over the analysis of internet searches before last year's Mannheim attack.
"The results from Google Trends are unsuitable for presented analysis and evaluation methods and cannot be used with validity either," the spokesman told Reuters.
The spokesman suggested that the the results were based on samples and searches that were too small, and that VPNs (Virtual Private Networks) that disguised the location of a search would not have been taken into account.
Despite the wariness of the intelligence response, former BND employee Gerhard Conrad warned that it would be "naive" not to pursue these leads.
Such violent crimes would certainly fit the "toolbox of what we now called hybrid measures, hybrid warfare", he said.
The domestic intelligence service warned only last week that Russian spies were using "espionage, sabotage and exertion of influence, including disinformation" to target Germany and the rest of Europe.
