“Crimes like today's strengthen our resolve to work with all Afghans who want peace to return to their country in 2018,” said Toby Lanzer, the acting head of UNAMA.
The attack occurred in Kabul's Qalai Nazir neighbourhood, a predominantly Shi'a Muslim area, hitting the Tabayan Cultural Centre where civilians had gathered to commemorate a national day.
So far, about 100 casualties have been reported, including scores of civilians killed. There are, however, fears the number may rise. Preliminary findings also indicate many children among the casualties.
Human rights teams from the UN Mission are on the ground to establish the facts.
In the release, Mr. Lanzer also expressed his sympathies with the families of those killed in the incident.
According to UNAMA, the Islamic State of Iraq and the Levant (ISIL or Da'esh), claimed responsibility for the attack. The Taliban issued a communique denying any involvement.