"Fourteen people were killed and at least 24 wounded," a police captain said of the Tuesday night bombing in the Baladruz area of Diyala province, north of Baghdad.
A medical source at the Baladruz hospital confirmed the toll.
The bomber struck "a gathering of notables and figures, most of them from the Al-Nida tribe," the officer said.
An army colonel said that the Al-Nida -- a major Sunni tribe in Diyala province -- had supported the government against Islamic State (IS) group jihadists.
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The jihadist group is made up of Sunni Muslims, but does not hesitate to attack Sunnis who oppose it.
Iraq announced in January that Iraqi forces had "liberated" Diyala, significant parts of which had been overrun by IS after the jihadists launched a brutally effective offensive last June.
But even if IS no longer fully controls towns in Diyala, jihadists can still carry out deadly bombings in the province, as they have for years.