The private Afghan Tolo News channel, quoting an eyewitness, reported that the explosion occurred in the Faraji Alaeddin area of the city.
Emergencies, a non-governmental organization that provides free medical and surgical treatment to Afghan civilians, said in a tweet on Twitter that 20 wounded people were treated in hospital after the blast.
A deputy UN spokesperson said on Friday that at least two UN staff members and their families were inside the Khalifa Sahib Mosque at the time of the attack.
Farhan Haq said he condemned the attack “in the strongest terms,” describing it as “the latest in a series of indiscriminate attacks on civilian targets.”
In a statement posted on Twitter on Friday, Taliban spokesman Zabihullah Mujahid also said He said he condemns the attack, which took place days before the end of the month of Ramadan.
“We strongly condemn today’s explosion in a mosque in the sixth district of Kabul,” Mujahid wrote on Twitter on Friday. “The brutal killings during this fasting are the work of circles that have nothing to do with Islam or the state.”
He added, “The Islamic Emirate extends its deepest condolences to the families of the victims, and the perpetrators of these crimes will soon be found and punished, God willing.”
Weeks of deadly attacks
A series of deadly explosions targeting mainly Shiite Hazara The community, many Afghan cities have been shaken over the past two weeks.
Mujahid, a Taliban spokesman, said 33 people were killed last week and dozens wounded in an explosion at a mosque in Afghanistan’s Kunduz province during Friday prayers.
This explosion followed other attacks in the previous days – one in the northern Afghan city of Mazar-i-Sharif and another in Kunduz, along with several explosions earlier in the week at a secondary school and education center in western Kabul.
Most of the recent attacks were claimed by ISIS affiliated organization and opponent of the Taliban, ISIS-Khorsan (ISIS-K). No group has claimed responsibility for Friday’s blast.
CNN’s Mostafa Salem, Nicola Karim and CNN’s Hannah Ritchie contributed to this report.