Germany's railway network has been targeted by apparent arson attacks just weeks before the country is set to host the Group of 20 summit in Hamburg, with authorities suspecting a political motive.
Some trains were canceled early Monday and travelers faced delays due to around a dozen deliberately set fires nationwide, according to initial investigations.
Federal police said train infrastructure was affected in Berlin, Hamburg, Cologne, Dortmund, Leipzig and other places.
Germany's state security department, responsible for investigating politically motivated crimes, has taken over the investigations in the affected regions.
An anonymous claim of responsibility has been published on a far-left leaning website.
The group which called itself "Shutdown G20: take Hamburg offline!", said it had struck rail tracks which it described as "the central nervous system of capitalism".
Similar sabotage action hit Germany in 2011, believed to be carried out by leftist extremists then protesting against the German military's deployment in Afghanistan.
Germany hosts on July 7-8 a summit of the Group of 20 biggest economies in the northern city of Hamburg, with leaders including US President Donald Trump and Chinese leader Xi Jinping due to attend.
Left-wing extremists have repeatedly called for protests and attacks ahead of the G20 summit on July 7-8, during which U.S. President Donald Trump and other world leaders will descend on the northern port city.
