Germany

Investigators reportedly have "significant doubts" about the authenticity of letters claiming responsibility for this week's bomb attack on German football club Borussia Dortmund's bus.

Three still-unverified confession letters found at the scene of Tuesday evening's blasts had suggested an Islamic extremist motive.

However a report commissioned by investigators - reported by German broadcasters NDR, WDR and newspaper Sueddeutsche - said detectives now question whether the letter was really written by Islamists.

German prosecutors confirmed on Thursday that a man detained in connection with the bus attack is believed to be a former commando unit leader for the so-called Islamic State in Iraq.

Two men and a woman have reportedly been arrested in Germany on suspicion of being part of a plot to attack police with explosives.

The suspects, a 27-year-old Afghan, a 27-year-old Turk and a 25-year-old German, were held in the northern town of Celle, German magazine Focus reported, citing the local chief public prosecutor.

The report said the trio were arrested on Thursday evening on suspicion of supporting a suspected Islamist militant and helping to prepare a "serious act of violent subversion against the state".

The suspected Salafist militant they are suspected of supporting remains in custody after being arrested in February.