Kabul has suffered repeated suicide attacks in recent weeks.
The sources said 30 others were wounded in the explosion.
The attack occurred during a morning panel discussion on the anniversary of the Soviet invasion of Sunni-majority Afghanistan at the Tabian Social and Cultural Centre, witnesses said.
The bloodshed followed an attack on a private television station in Kabul last month that was also claimed by the local affiliate of the Islamic State.
Afghan President Ashraf Ghani condemned the attack and ordered an investigation into the blast, a statement from the presidential office said.
The IS group has gained ground in Afghanistan since it first appeared in the region in 2015 and has scaled up its attacks in Kabul, including on security installations and the country's Shiite minority.
But high-profile attacks in the big cities have continued as militants have looked for other ways to make an impact and undermine confidence in security.
"We can confirm that so far 11 bodies have been brought to our hospitals as well as 25 wounded", the AFP news agency quoted Health Ministry spokesman Wahid Majroh as saying on January 4.
Police officers at the scene said the bomber had been wearing police or army uniform and had approached a group of security personnel conducting controls on illegal drugs and alcohol sellers, but there was no official confirmation.