At least 60 people have been killed at a funeral in the mainly Shia Muslim Sadr City district of the Iraqi capital, Baghdad.
A tent where mourners were gathered was hit by two explosions, one of them a suicide car bomb.
A third explosion followed as police, ambulances and firefighters gathered at the scene, according to one report.
Officials reported that women and children were among the dead and that more than 120 people had been injured.
No group has claimed responsibility for the bombing, which happened early on Saturday evening.
The explosions reportedly set the tents and nearby cars on fire, with eyewitnesses describing the scene as an "inferno".
"I saw several charred bodies on the ground and tents on fire and also burning cars. Wounded people were screaming in pain,'' says one of the mourners, Sheikh Sattar al-Fartousi.
Medics in nearby hospitals confirmed the scale of the casualties.
Also on Saturday, eight people were killed in a separate bomb attack in a street in the nearby neighbourhood of Ur.
And at least five police officers were killed in an assault on a police station in Baiji, north of Baghdad.
Surge in violence
Sectarian violence has surged across Iraq in recent months, reaching its highest level since 2008.
The violence was triggered in April by an army raid on a Sunni Muslim anti-government protest camp near Hawija, also north of Baghdad.
The country has also seen a spill-over of violence from the conflict in Syria, which has taken on increasingly sectarian overtones.
In recent weeks, Iraqi security forces have reportedly arrested hundreds of alleged al-Qaeda members in and around Baghdad as part of a campaign which the Shia-led government is calling "Revenge for the martyrs".
But the operations, which have taken place mostly in Sunni districts, have angered the Sunni community and failed to halt the violence.
More than 5,000 people have died so far this year in Iraq, 800 of them in August alone, according to the United Nations.