Ghani tweeted: "I condemn the heinous terrorist attacks in Kabul and Pul-e-Khumri. 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."

Afghanistan's CEO Abdullah Abdullah also strongly condemned the incident.

He tweeted: "I strongly condemn the terrorist attack on voters' registration center in Kabul. 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."

Apart from leaders in Afghanistan, NATO and the US also joined the nation in condemning the latest terror attack in the capital city.

"I strongly condemn the attack on a voter registration centre in Kabul. #NATO stands with #Afghanistan in the fight against terrorism and for democracy," tweeted NATO Secretary General Jens Stoltenberg.

US Ambassador John Bass offered his condolence to the victims of the attack.

"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," he posted.

At least 31 people were killed in a suicide attack on a voter registration centre in the Dasht-i-Barchi area of Afghanistan's Kabul city on Sunday, media reports said.

The incident left 54 others injured.

Hashmatullah Stanikzai, a Kabul police official, told Pajhwok Afghan News the explosion happened when a suicide bomber targeted civilians who had gathered to receive identity cards at 10am.

Dr. Wahid Majroh, spokesman for the Ministry of Public Health, told the news agency 31 dead and 54 injured individuals had been evacuated to hospitals from the blast site.

Police have blocked the road which led to the blast site.

According to reports, huge explosion was heard across the city.

Several vehicles have been reportedly damaged, reports said.

No group has claimed responsibility for the attack so far.

Terrorism-hit Afghanistan in 2018:

Afghanistan has witnessed several terrorism-related attacks this year.

Armed conflict in Afghanistan killed 763 civilians and injured 1,495 in the first three months of this year, the United Nations mission in the country said recently.

“All parties to the conflict in Afghanistan must do everything in their power to protect civilians from harm,” said Ingrid Hayden, the Secretary-General’s Deputy Special Representative for Afghanistan. “Afghan civilians continue to suffer, caught in the conflict, in ways that are preventable; this must stop now.”

The 2,258 civilian casualties, documented from 1 January to 31 March by the UN Assistance Mission in the country, known as UNAMA, are at the similar levels recorded in the first three months of 2017 and 2016. Anti-Government elements caused 1,500 civilian casualties, up six per cent from the same period last year.

Suicide improvised explosive devices (IED) and complex attacks were the leading cause of civilian casualties – a new trend. The Mission found that combats on the ground were the second leading cause, followed by targeted and deliberate killings, explosive remnants of war, and aerial operations.