Law enforcers in Germany are investigating a string of arson attacks that hit the intercity rail tracks yesterday in what could be protest actions by left-wing extremists ahead of the G20 summit in July.
Police said cable ducts of rail signaling equipment were set on fire in the states of Lower Saxony, Berlin, North Rhine-Westphalia and Saxony.
"A political motive in relation to the G20 summit in Hamburg is not ruled out," they said in an appeal for eyewitnesses.
In all, 12 cases of arson were reported, with the perpetrators believed to have struck between 1 a.m. (2300 GMT) and 4:30 a.m. (0230 GMT).
Services in several locations including the eastern cities of Leipzig and Dresden as well as long-distance lines linking Berlin and Prague were disrupted, rail operator Deutsche Bahn said.
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 acts of sabotage hit Germany in 2011, believed to be carried out by leftist extremists then protesting against the German military's deployment in Afghanistan.
Northern Germany's port city of Hamburg hosts a summit of the Group of 20 biggest economies in the northern city of Hamburg on July 7-8.
World leaders including U.S. President Donald Trump and Chinese leader Xi Jinping are due to attend.
Hamburg has increased its security measures in preparation for the upcoming event after far-left activists threatened attacks ahead of the summit.
The security measure includes border controls, which will be carried out at various locations with temporal flexibility.
For security officials, however, questions remain over whether protesters or potential terrorists will disrupt the summit.
In this respect, the Federal Criminal Police Office (BKA) announced that it was expecting numerous demonstrations across the city. According to German media sources, about 15,000 police officers from across Germany will be recruited for the event in Hamburg.
"We must assume that a considerable amount of people in Hamburg will have the goal of disturbing the event," BKA President Holger Münch told the "Berliner Zeitung" emphasizing that the Hamburg police had prepared its units for possible violent protests.
There have also been protests at previous events including the opening of the European Central Bank in Frankfurt in 2015, Münch said, adding that thousands of demonstrators ready for violence were generally expected in such cases.