German police have made one arrest, and are probing a possible “Islamist link” to three explosions that rocked the Borussia Dortmund football team bus after a letter found at the scene referred to the Berlin Christmas market attack, national media reported Wednesday. 

German federal prosecutor also said the arrested suspect has a "terrorist background", local media reported.

"Two suspects from the Islamist spectrum have become the focus of our investigation. Both of their apartments were searched, and one of the two has been detained," said lead prosecutor Frauke Koehle.

‍Three explosions rocked the Borussia Dortmund football team's bus, injuring Spanish international player Marc Bartra, as the German team headed for a Champions League game against AS Monaco on Tuesday.‍

Bartra underwent wrist surgery after being hit by flying glass, and the quarter-final match was postponed until Wednesday because of the attack. The club said the other Dortmund players were "shocked" but safe.

The bus had set off for the Borussia stadium about 10 kilometres away when "three explosive charges detonated," said police.

The explosives, which went off shortly after 7:00 p.m. local time, were hidden in a hedge and were set off as the bus passed. The blast shattered the bus windows and the vehicle was burned on the right hand side.

"The bus turned into the main street, when there was a huge boom, a real explosion," Sky television quoted Dortmund goalkeeper Roman Burki as saying.

"I was sitting in the back row next to Marc Bartra, hit by fragments ... after the bang, we all ducked."

"At this time, it is still not clear what the real background to this act is," Dortmund police chief Gregor Lange told a late night news conference in the western German city.

Lange said police assumed the team bus was deliberately targeted in the attack as it left the team hotel on the way to the stadium.

Police earlier said there had been no risk to the Signal Iduna Park stadium, the largest in Germany, holding more than 80,000 fans, where the first leg of the quarter-final of Europe's top club soccer competition was due to have been played.

"The explosive devices were placed outside the bus. Several windows were broken," a police spokesman said. The incident was in the Hoechsten district in the south of the city of Dortmund.

Borussia Dortmund's managing director Hans-Joachim Watzke was quoted as telling Sky, "The whole team is in a state of shock."

AS Monaco goalkeeper Danijel Subasic told Croatian newspaper 24sata: "We are currently in the stadium, in a safe place, but the feeling's horrible."

Dortmund and UEFA said the match would go ahead on Wednesday at 4:45 p.m. local time.

“The thoughts of every one of us at FIFA are with the people of Dortmund, and the fans of both Borussia Dortmund and Monaco following today’s troubling events," FIFA President Gianni Infantino said. 

(Source: Reuters, AFP)