The Syrian man who blew himself up in Germany wounding 12 people was supposed to be sent back to Bulgaria after his protection request had been rejected, German officials say.

Why the development did not take place was not immediately clear, according to a spokesperson of Germany's Federal Interior Ministry.

Deportation of asylum seekers whose requests are turned down lies with the German "states" and not federal authorities.

“Syrians cannot at the moment be deported to Syria at the moment, but that doesn’t mean that Syrians overall cannot be deported,” The Guardian quotes ministry spokesperson Tobias Plate as telling a regular government news conference.

Earlier, German- and English-language media had reported that the 27-year-old Syrian national had made two suicide attempts after being denied protection.

Separately, German media quoted Bavarian Interior Minister Joachim Herrmann as saying there was an "Islamist" motive in the attack, a claim that was later downplayed by police officials as the latter's "personal view".