The bomb exploded in a tent filled with about 150 mourners who had gathered for the funeral procession of a leader of the Zubaidi Shia tribe in the northern city of Baqouba on Monday.
An army first lieutenant, four police officers, and seven security forces were among the dead.
Hospital sources in Baquba told Arab media that there are over 30 bodies inside the morgue.
Sami al-Massudi, a Shiite official who oversees the well-being of Shiite religious sites in Iraq, said late Monday that a roadside bomb hit his convoy in Saidiyah area of south Baghdad, wounding three of his bodyguards
The attack comes after five people were killed overnight on Monday in two car bombs in Ramadi, 120 kilometres west of Baghdad.
Explosions in Iraq last week claimed the lives of some 100 people, many of them Shiite pilgrims commemorating the martyrdom of Imam Mousa al-Kadhim at a shrine in northern Baghdad.
Earlier in the day, the convoy of Sami al-Massudi, the deputy director of the Shia Wafq (Shia Endowment) of Iraq was targeted by a roadside bomb in the Iraqi capital Baghdad.
The deputy director of the Shia Wafq, which is a government-run body that oversees Shia religious sites in Iraq, said the blast injured three of his bodyguards.
“Absolutely this is the way of al-Qaeda --targeting innocent people to ignite sectarian unrest,” said Sadiq al-Husseini, who is the chairman of the Diyala provincial council.
Violence has risen in Iraq since December 2011, when an arrest warrant was issued for fugitive Vice President Tariq al-Hashemi, who has been charged with running a death squad targeting Iraqi officials and Shia Muslims.