Gunmen attacked a ceremony in Kabul on Friday, killing at least 29 people in the first major attack on the Afghan capital since the Washington reached an agreement with the Taliban to withdraw US troops.
A top Afghan political leader, Abdullah Abdullah, was present at the event but escaped safely.
Up to 55 people were wounded, according to the Afghan ministry of health. However, a health ministry spokesman said the casualty toll could rise.
A NATO source said that the death toll was slightly higher: more than 30 killed, with 42 wounded, 20 of whom were in a serious condition.
"The attack started with a boom, apparently a rocket landed in the area, Abdullah and some other politicians ... escaped the attack unhurt," Abdullah's spokesman, Fraidoon Kwazoon, who was also present, told Reuters.
Dead and wounded were being ferried from the site by ambulance.
For his part, President Ashraf Ghani tweeted that the attack was "a crime against humanity and against the national unity of Afghanistan."
The Taliban have denied they were behind the attack.
The attack came just days after the US and the Taliban signed an ambitious peace deal that lays out a conditions-based path to the withdrawal of US forces from Afghanistan, the Associated Press reported.
Any US troop pullout would be tied in part to promises by the Taliban to fight terrorism and ISIS.
