Security reviewed at all Champions Leagues games

A police officer, who had been travelling on a motorbike in front of the bus, was also injured.

"The prosecutor's office confirms the discovery of a letter near the scene of the crime".

UEFA president Aleksander Ceferin expressed his distress at the scenes in Dortmund and praised the decision to postpone the match until Wednesday. Several of the vehicles' window panes were broken.

The police has yet to figure out the reason behind the attack.

"After the initial investigation, we assume that this was an attack using serious explosives", unidentified Dortmund police officials told Reuters.

Despite the apparent claim of an Islamic motive, the attack does not have much in common with previous incidents of that type, the BBC's correspondent in Berlin, Damien McGuinness, said.

Ralf Jaeger, the interior minister for North Rhine-Westphalia state, said security had been stepped up in Dortmund, including at the club's training ground and stadium.

Police are reported to be investigating a possible "Islamist link" to an attack on the Borussia Dortmund team bus, according to reports. "The bus turned onto the main street when there was a huge bang - a proper explosion", Burki said in the interview. "I think the team will feel it tomorrow".

Swedish couple say 11-year-old daughter died in truck attack
Legal documents show Akilov had asked for Eriksson to be replaced by a Sunni Muslim lawyer, but the court denied his request. However, this man would remain in custody due to an earlier decision that he be expelled from Sweden, the authority said.

"Borussia Dortmund is especially strong in extreme situations".

One of the Dortmund players, Mathias Ginter, was involved in the Germany-France match that was targeted in the terror attacks in Paris on 13 November, 2015. Another present in Paris, Andre Schurrle, was injured for the Monaco match.

Lücke said: "At 19:15 CET, there were three explosions in the vicinity of the hotel in which the BVB team had been guests and were leaving to travel to the stadium".

"I was deeply disturbed by the explosions which occurred in Dortmund", he said in a statement.

Thomas Tuchel's team were due to play Monaco at home in the first leg of their Champions League quarter-final tie, but it was called off and rescheduled for 5.45pm United Kingdom time today.

And the Chancellor of Germany has now been in touch to express her support.

Dortmund are now fourth in the German Bundesliga table.