German police have raised the terror threat level after warnings of more attacks on high-profile events, including football games and concerts, following last week’s bombing in Dortmund.

Police said military-grade explosives were used to target the bus of the city’s football team. They believe that these were planted by members of the far right rather than by Islamists.

The pipe bombs, filled with shrapnel, exploded near Dortmund’s vehicle, injuring the Spanish defender Marc Bartra and a police officer.

An official document leaked to Die Welt newspaper yesterday suggested the bombers wanted to incite a backlash against Muslims. Three letters found nearby, which claimed the bombing on behalf of Islamists, were fabricated, said the investigators.

“The explosive in the pipe bombs, which were filled with metal