A suicide blast killed 48 people -- including five children -- and wounded over 100 more on Sunday at a voter registration center in Kabul, according to Afghan officials.
The bomber was on foot when he detonated his explosives at the gate of the building about 10 a.m. local time, Interior Ministry spokesman Najib Danish said.
ISIS claimed responsibility for the bombing, in a statement distributed through Telegram. ISIS said "our martyrdom brother" targeted a group of Shiite people outside the voter registration center in the Dashte Barchi neighborhood.
Registration for October's parliamentary and district council elections in Afghanistan opened April 14.
Resolve for 'fair and transparent election'
In a message posted to Twitter, the nation's chief executive Abdullah Abdullah condemned the attack.
"I stand with those affected by this coward attack. Our resolve for fair and transparent election will continue and terrorists won't win against the will of the Afghan people," Abdullah said.
President Ashraf Ghani said the Kabul attack and another reported in Pul-e-Khumri were "heinous terrorist attacks."
"I wish Allah's mercy upon those who martyred, speedy recovery to the wounded, and convey my deep condolences to victims' families. I instructed relevant institutions to provide support and care to those affected," Ghani said on Twitter.
US Ambassador John Bass said the Kabul attack was "senseless."
In a statement posted on Twitter, Bass said: "I strongly condemn this morning's suicide attack on a voter registration center in #Kabul and offer my condolences to the victims and their families. This senseless violence shows the cowardice and inhumanity of the enemies of democracy and peace in #Afghanistan."
British ambassador Nicholas Kay tweeted his condolences to the victims, saying that "the enemies of peace & democracy will not win."
The attack is the latest in a series to strike the Afghan capital this year.
On March 21, a suicide bomber killed 29 people and injured 52 others near a shrine in the city in an attack claimed by ISIS. Earlier that same month, a suicide bomber killed at least nine people when he detonated his device at a security checkpoint.
In February, several people were killed and injured in a suicide attack in the Shashdarak area of Kabul, not far from the Kabul Green Zone where many diplomatic compounds are located.
Days later, the group claimed responsibility for an attack outside a hospital in which militants detonated explosives packed inside an ambulance. Nearly 100 people were killed.
The Afghan government announced on February 28 it would be willing to recognize the Taliban as a legitimate political party as part of a potential ceasefire agreement with the Islamist militant group.