A bomb struck near the entrance of the large Eidgah mosque in Kabul Sunday during the memorial service for the mother of Zabihullah Mujahid, the Taliban spokesman.
AFP news agency reported at least two people were killed, citing Qari Sayed Khosti, a spokesman for the Interior Ministry. The Italian-run NGO Emergency, which operates a hospital in Kabul, said on Twitter it was treating four people wounded in the blast.
Outside the hospital, medical staff waited as people in blood-sprayed clothes arrived.
Mujahid said "a number of civilians" were dead.
Ahmadullah, a shopkeeper nearby, told AFP, "I heard the sound of an explosion near the Eid Gah Mosque followed by guns firing."
Mujahid had earlier announced on Twitter that "all people and friends are invited to attend" the memorial for his late mother.
Following the blast, the Taliban cordoned off the area and maintained a heavy presence.
No one claimed responsibility for the blast, though IS-K has claimed several attacks against the Taliban, including in Jalalabad. The terror group maintains a presence in the province of Nangarhar, where Jalalabad is located, and considers the Taliban an enemy.
IS-K attacks in Kabul have so far been rare. On Friday, the Taliban raided an IS safehouse north of Kabul in Parwan province after a roadside bomb injured four Taliban fighters.