A Taliban fighter stands guard near the site of a blast in Kabul on April 29, 2022. AFP
"The Secretary-General strongly condemns yesterday's deadly attack on the Khalifa Sahib Mosque in western Kabul during Friday prayers," a spokesperson for Antonio Guterres said in a statement.
"He extends his deepest condolences to the families of the victims and wishes a swift recovery to those injured. Attacks against civilians and civilian objects, including mosques, are strictly prohibited under international humanitarian law."
The target of the blast appeared to be members of the minority Sufi community who were performing rituals after completing Friday prayers, an official said.
Grisly images of the blast posted on social media showed survivors running out of the mosque, with some carrying victims including children. Patches of blood could be seen on the floor of the mosque compound.
Interior ministry spokesman Abdul Nafi Takor said at least 10 people were killed, while Kabul police said another 30 were injured.
The bombing was the latest in a wave of attacks that have rocked Afghanistan during the fasting month of Ramadan.
Dozens of civilians have been killed in the primarily sectarian attacks -- some claimed by the Islamic State group -- targeting members of the Shiite and Sufi Muslim communities.
Friday's blast comes a day after two bombs on separate minibuses killed at least nine people in the northern city of Mazar-i-Sharif, targeting Shiite passengers heading home to break their Ramadan fast.
A bomb at a Shiite mosque in Mazar-i-Sharif a week earlier killed at least 12 worshippers and wounded scores more.