Police in Dortmund said the blasts were believed to be “an attack with serious explosive devices”.

It is believed the bombs could have been placed in a hedge near a car park.

Police said an explosion burst one of the vehicle’s windows and injured one player, Barta, who was taken to hospital with a hand injury.

Dortmund’s Swiss goalkeeper Roman Buerki told the Swiss newspaper Blick:

“I was sitting in the back row next to Marc Bartra who was hit by shards from the burst back window.

“The bus had turned onto the main road when there was a big bang — a real explosion.”

The incident came as the Dortmund squad left the team hotel for the Champions League quarter-final match against French side Monaco.

The match was postponed until Wednesday.

Dortmund chief executive Hans-Joachim Watzke told Germany’s Sky television:

“The team and the coaching staff are of course shocked. We must now channel it in some way,” he said.

“It will not be easy to get that out of the mind. In such a crisis situation, all at Borussia pull together. I think the team will feel it tomorrow.”