Early on Monday morning, arsonists attacked rail lines in 12 different locations.
Cable ducts of rail signalling equipment were set on fire in the states of Lower Saxony, Berlin, North Rhine-Westphalia and Saxony, police said.
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.
Berlin police are investigating a claim of responsibility which was posted on a left-wing website on Monday morning. Sources inside the police department say the letter “fits the bill”, but caution that it is too early to tell if it is authentic.
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.
A fire near Treptower Park station in eastern Berlin resulted in damage to electricity cables, leading officials to deploy replacement bus services, including for the main S-Bahn route into the city from Schönefeld Airport, Tagesspiegel reports.
Focus reports massive delays in the area of Leipzig, where several arson attacks hit commuter services around the city.
"In some cases, arson devices could be disarmed before they caused damage," a spokesperson for the federal police told Focus.
State security services, which are responsible for investigating politically motivated crimes, have taken over the investigations.
The arson reports come weeks before the G20 summit is to be held in Hamburg on July 7th and 8th. The summit of political leaders from the world's major economies is often accompanied by violence from fringe left-wing groups.