An attempted arson attack on a Berlin railway was foiled today, the third in two days targeting rail operations in and around the city.
A railway worker found three bombs on cables along a track in eastern Berlin and they were defused by police experts.
An arson attempt Monday on Berlin's central station using seven bottles filled with flammable liquid bundled together and linked to a fuse was thwarted at the last minute.
A similar device exploded in a utility shaft next to a high-speed train line west of Berlin a few hours earlier, causing damage but no casualties, and halting train traffic there for the day.
It was still unclear whether the attacks were related.
A previously unknown left wing group claimed responsibility for Monday's attacks in a letter whose authenticity was being examined by police.
In a message posted on a website, a group calling itself Hekla Reception Committee - Initiative for more Eruptions in Society claimed responsibility, saying it was targeting railway operations to protest at Germany's roles in the Afghanistan war and as an arms exporter. The group's name is an apparent reference to Iceland's Hekla volcano.
Berlin has seen several recent arson attacks that police have blamed on leftist extremists. One of them in May targeted a utility shaft at an important railway hub in the city's east, causing massive disruption that left thousands of passengers stranded.
Germany is a large contributor to the Nato-led International Security Assistance Force in Afghanistan, with about 5,000 soldiers stationed in the north of the country.