A German citizen of Somali origin was behind Sunday's bomb attack on Jazeera Hotel in Somalia's capital Mogadishu that killed 15 people, a senior Somali intelligence officer said Wednesday.

"Full investigations are still continuing and it is too early to give full update, but what I can confirm to you is that the male bomber was a German citizen of Somali origin who just came back (to Somalia) recently," the unnamed officer told Xinhua, noting that the suicide bomber had lived in the German city of Bonn before his return to Somalia.

Sunday's blast has been described as one of the worst scenes of destruction seen in Mogadishu. Somalia-based militant group Al-Shabaab has claimed responsibility for it.

Omar Sharif, a Somali hotel owner, said he thought the increased terror attacks in the country were often carried out by radicalized young Somalis living abroad, including those in Europe and North America.

In June, a British Muslim convert, Thomas Evans, was among Al-Shabaab militants killed in their raid on a Kenyan army camp.

Al-Shabaab said the new wave of attacks was responding to recent operations by African Union forces and the Somali troops.