The bomber targeted a delegation from the minority communities as it was travelling to the governor’s residence in the eastern city of Jalalabad on Sunday for a meeting with President Ashraf Ghani.
Avtar Singh Khalsa, a longtime leader of the Sikh community, was among those killed. Another 20 people were wounded.
In a statement released Monday, IS said it had targeted a group of “polytheists.”
Sikhs and Hindus face discrimination in the conservative Muslim country and have been targeted by Islamic extremists in the past, leading many to emigrate. The community numbered more than 80,000 in the 1970s, but today only around 1,000 remain.
A suicide bombing in the eastern Afghan city of Jalalabad has killed at least 19 people, most of the members of the country’s Sikh minority.
Police said they had been travelling in a vehicle to meet President Ashraf Ghani, who is visiting Nangarhar province when the bomber struck.
Among those killed was the only Sikh candidate who had planned to contest October’s parliamentary elections.
The Islamic State (IS) group said it carried out the attack.
Hours earlier, Ghani had opened a hospital in Jalalabad during his two-day visit to Nangarhar. Officials said he was not in the area when the suicide blast occurred.
The Indian embassy in Kabul condemned the “cowardly terrorist” attack.
It confirmed that Awtar Singh Khalsa, the only Sikh candidate running in the 20 October elections, was among the dead.
“The attack underlines the need for a united global fight against international terrorism without discrimination and accountability of those who support terrorists in any manner,” the embassy tweeted.
Nangarhar health director Najibullah Kamawal said that 17 of the dead were Sikhs and Hindus. Another 20 people were wounded, he added.