Germany's Foreign Ministry says a German man believed to have been kidnapped in Cameroon by the Islamic extremist group Boko Haram has been freed.

Foreign Ministry spokesman Martin Schaefer said the man, whose name was not released, is now in safety in Cameroon's capital. He refused to specify how the man was released, and said he did not have details of his condition, beyond that he was healthy enough to be transported.

The man was kidnapped last July, allegedly by the Nigerian-based Boko Haram group, though it remains unclear where he was seized.

Schaefer said a crisis team had been working on the case for months, and he thanked the Cameroon government for its "very good and trusting" cooperation during the ordeal.