According to an AP report in USA Today:
The German Interior Ministry said Tuesday that the Islamic Jihad Union militant group has taken responsibility for planning last week's foiled terror bombings in Germany, adding that the U.S. air base at Ramstein was a target as well as U.S. and Uzbek consulates in Germany.
The report further notes that "The Islamic Jihad Union is described by police and prosecutors as an offshoot of the Islamic Movement of Uzbekistan, a militant group which had origins in that Central Asian country. The IJU has been designated a terrorist organization by the U.S. State Department...."
The group used the Internet to make its announcement.