The death toll rose to at least 57 after a suicide bomber unleashed an attack Sunday at an Afghan voter registration center in mostly poor area of Kabul. An Islamic State affiliate claimed responsibility for the massacre.

Health Ministry spokesman Wahid Majroh told Pajhwok Afghan News the dead included 21 women and five children. He said 119 people were injured in the attack.

Abdullah Abdullah, the nation's chief executive, condemned the attack in the Dasht-i-Barchi neighborhood.

"I stand with those affected by this coward attack," he tweeted. "Our resolve for fair and transparent election will continue, and terrorists won't win against the will of the Afghan people."

Police Spokesman Hashmatullah Stanikzai said the bomber targeted civilians who had gathered to register and obtain ID cards. Elections are schedule for October. 

The explosion, heard across much of the city, damaged several nearby vehicles and shattered windows miles away. Police blocked all roads leading to the site, with only ambulances allowed in. Witness Bashir Ahmad told Al Jazeera he heard a bang and rushed to the site of the blast.

"When I arrived at the scene, we helped many wounded people by carrying them to hospital," he said.

It was the fourth attack on an Afghan voter registration center in less than a week, authorities said. On Friday, militants attacked a center and killed a security officer in Qala-e-Naw, in Badghis province.

On Thursday, armed men attacked two police officers  in Jalalabad City who were guarding a voter registration center. And on Tuesday, militants attacked a center in Ghor province, kidnapping three election officials and two police officers.

The U.S. and NATO ended their formal combat mission in Afghanistan more than three years ago. Insurgents have made strides in undermining government security forces in recent months. The increasing violence has cast doubt on whether secure elections can be held in the fall.

Afghan President Ashraf Ghani ordered government agencies to provide aid to the victims of the "heinous terrorist attacks" Sunday in Kabul and, about two hours later, in Pul-e-Khumri, where at least five people were killed by a roadside bomb.

He stressed that the attacks won't derail the democratic process.

"I wish Allah’s mercy upon those who martyred, speedy recovery to the wounded, and convey my deep condolences to victims’ families," Ghani said.