According to reports, the incident left 117 others injured.

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

Police had earlier 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.

Attack triggers widespread condemnation:

Afghanistan President Ashraf Ghani on Sunday condemned the suicide attack which claimed 31 lives in Kabul city and left 54 others injured.

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.

The suicide attack on a voter-registration centre in the Afghan capital Kabul which left at least 30 dead on Sunday, has been condemned by the UN mission in the country, UNAMA.

“The UN family in Afghanistan feels a deep sense of revulsion at today’s outrage,” said the head of the mission, Tadamichi Yamamoto, adding that “the killing appears to be part of a wholly unacceptable effort by extremists to deter Afghan citizens from carrying out their constitutional right to take part in elections.”

India and Pakistan also condemned the incident.

India said the incident reflected that it was an attack on the democratic rights of the Afghan people.

"India strongly condemns the cowardly and barbaric terrorist attack in Kabul and Baghlan today," the Ministry of External Affairs said in a statement.

"What makes this attack particularly reprehensible is the fact that the terrorists and their backers chose to attack a voters’ registration centre for the upcoming parliamentary and district council elections. The attack has resulted in the death of Afghans who firmly support and believe in the democratic process to empower themselves and make their voice heard. This is not only an attack on innocent civilians but also an attack on the democratic rights of the Afghan people," it said.

"Our thoughts and prayers are with the family members of the victims, and we wish quick and complete recovery to the injured. India stands ready to extend all possible assistance, including for treatment of those injured," it said.

Pakistan's Ministry of Foreign Affairs said in a statement: "Pakistan strongly condemns the heinous and reprehensible suicide attacks that targeted innocent civilians at voter registration centres in Kabul and Baghlan provinces in Afghanistan, today.We are grieved at the loss of precious innocent lives in this brutal act of terrorism."   

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.

Image: UN website