The bomber detonated his explosives on Thursday evening in a house near the town of Balad as a group of Sufis gathered for a religious ceremony, Interior Ministry officials said. is a system of esoteric philosophy commonly associated with Islam. In modern language it might also be referred to as "Islamic spirituality" or "Islamic mysticism".
The central concept in Sufism is love. Dervishes - the name given to initiates of Sufi orders - believe that love is a projection of the essence of God to the universe.
Many Sufi practitioners are organized into a diverse range of brotherhoods and sisterhoods. Many orders can be classified as Shia or Sunni and in some cases, even both.
Until Thursday's blast, Iraq's Sufi community had been spared major attacks.
In Kirkuk, where ethnic tensions have been building between
Kurds, Arabs and Turkomen who all lay claim to the strategic oil city, armed men killed a leading Turkoman official in a drive-by shooting as he left Friday prayers, police said.
The victim, Brigadier Sabah Bahlul Qara al-Tun, an assistant director of interior affairs at the council for Kirkuk province, was killed after performing Friday prayers at Hussam al-Din mosque.
Imams of mosques condemned
recent US military operations
Qara al-Tun is a prominent figure at the Turkman Front.
US base targeted
Also on Friday, Iraqi police sources in the northern city of Tikrit said seven Iraqi national guards were seriously wounded in a car bomb blast targeting their patrol at the northern entrance of a US military base in the centre of the city.
US and Iraqi forces have sealed off the area, and witnesses said ambulances were seen rushing to the scene and evacuating the wounded to Tikrit's general hospital.
Hundreds of Iraqis protested against US forces' detention of a political leader, while some imams in their sermons slammed the US for its security operation.
Protesters on Friday carried Islamic Party banners and signs denouncing the seizure of party leader Mohsen Abd al-Hamid and his three sons on Monday, calling it "American terrorism".
"During this operation they arrest our sons for the simple fact of being Sunnis"
Sheikh Iyal al-Ezzi,
All four were later released.
"Go Home American Forces", another banner proclaimed, saying the troops had shamed themselves.
The US military admitted to having detained Hamid in what they said was a mistake.
But the forces have yet to publish an apology or give the reason for the operation, during which the Sunni leader was taken hooded and handcuffed from his home.
A member of the Islamic Party's politburo, Sheikh Iyal al-Ezzi, led a Friday prayer and slammed Operation Lightning, an Iraqi government offensive backed by the US.
"During this operation they arrest our sons for the simple fact of being Sunnis," he said, adding that the assault had "culminated with the aggression against one of our symbols, Mohsen Abd al-Hamid".
Al-Ezzi warned Iraqi authorities not to sideline Sunnis and urged all Iraqis to unite.