The UN Secretary-General Antonio Guterres on Sunday night condemned the attack on a population registration center in Kabul city that killed 57 people.
Guterres said in a statement that the culprits must be brought to justice.
"They must not be allowed to succeed in deterring Afghan citizens from carrying out their constitutional right to take part in forthcoming elections."
He extended condolences to the families and expressed solidarity with the Afghan government.
This comes after a suicide bomber detonated explosives outside the center where dozens of people had been waiting to get ID documents.
In addition to the 57 killed, more than 100 people were wounded.
Officials said the casualties were all civilians – many of them women and children.
Exact figures on how many people had been waiting were not available but officials said that particular office had in recent days been processing about 100 ID (Tazkira) applications a day.
By Sunday mid-day, there had been five attacks in less than a week against the election process.
Two hours after the Kabul bombing, an explosion rocked Pul-e-Khumri city in Baghlan province, killing at least six people and wounding five others.
This explosion happened close to a voter registration center in the provincial capital, officials confirmed.
Last week three other attacks took place.
On Tuesday, unknown armed men attacked a voter registration center in Ghor province and kidnapped three IEC employees and two policemen.
Ghor police spokesman said the attackers were Taliban.
On Thursday, unknown armed men attacked two police force members in Jalalabad City who were guarding a voter registration center.
The two policemen were killed in the ensuing gunfight.
On Friday, unknown armed men attacked a voter registration center in Qala-e-Naw, the center of Badghis province, where a police officer assigned to maintain security was killed.