Dortmund attack 'false-flag operation to trigger backlash against Muslims'

The bombers responsible for an attack on the team bus of Germany's Borussia Dortmund football club may have attempted to incite a backlash against Muslims, an official document suggests.

Investigators say that three letters discovered near the attack, which claimed Islamists were behind it, were fabricated.

They added that the construction of the explosives suggests a worryingly high-level of expertise and resources.

"The explosive in the pipe bombs, which were filled with metal shrapnel, seems to derive from the inventory of the army. But we are still investigating that," a police source told the Die Welt.

Such military-grade detonators could only have been wired by an individual with "professional skills", the official said.

The pipe bombs, which exploded near the club's team bus, injured Spanish defender Marc Bartra and a police officer.

Police now believe that the bombs were planted by far-right extremists rather than Islamists.

"One of the most likely scenarios is that the attack had a far-right background," a police spokesman said.

In the past, Neo-Nazi groups have planted bombs in public places in Germany, including in 2004, when Turkish immigrants in Cologne were targeted. 

With Germany currently under its second-highest level  of threat alert, security services are still searching for leads on the perpetrators who are still believed to be at large.

Investigators are also looking into the possibility that the bus attack was perpetrated by far-left groups, "foreign intelligence" or lone wolf attackers.