“The Secretary-General strongly condemns the attack,” said his spokesman, Stéphane Dujarric, in a statement issued overnight.
“Attacks that deliberately target civilians are clear violations of fundamental human rights and international humanitarian law,” he added.
The UN Assistance Mission in Afghanistan (UNAMA) joined in the condemnation of the attack at the Jawadia mosque.
According to the Mission, two attackers entered the Shia mosque during the evening prayer time when several hundred worshipers were present, opening fire and detonating two suicide improvised explosive devices against the congregation.
“This attack deliberately targeting civilians at prayer can have no justification whatsoever,” said Tadamichi Yamamoto, the Secretary-General's Special Representative for Afghanistan. “Fanning terror and sectarian violence against a specific community is abhorrent and those responsible must be brought to account.”
The Secretary-General and UNAMA expressed condolences to the victims' families and wished a speedy recovery to the injured.
According to UNAMA, the attack is the fifth this year targeting Shia mosques, killing a total of at least 44 civilians and injuring at least 88. Four of the attacks occurred in Herat and the other in Kabul. Islamic State-Khorasan province claimed responsibility for two of these attacks.
In 2016, UNAMA recorded four separate attacks against Shia mosques and religious gatherings. Islamic State-Khorasan province claimed responsibility for two of those attacks.
Yesterday's attack took place one day after the assault against the Embassy of Iraq in Kabul, where two Afghan civilians lost their lives and one was injured.
The United Nations recalls international humanitarian law that prohibits deliberate attacks against civilians and civilian objects, including places of worship, as well as the cardinal principle of the inviolability of diplomatic premises.