Images from the scene show people lying in the snow in the street outside the central Kabul building.
“I don’t know how many of them were dead or injured,” AFP driver Jamshed Karimi said, adding: “I saw the man blow himself up.”
Kabul police spokesman Khalid Zadran confirmed the explosion “which unfortunately resulted in casualties”.
“Security teams have reached the area,” he tweeted.
The Taliban claim to have improved security since storming back to power in August 2021 but there have been scores of bomb blasts and attacks, many claimed by the local chapter of the Islamic State (IS) Daesh group.
The Islamic State jihadist group claimed responsibility Wednesday for a suicide bombing outside the foreign ministry in Kabul that officials and witnesses said killed at least five people and wounded 40 others.
An IS member slipped by Taliban security barriers “before blowing up his explosive belt in the middle of employees and guards,” the Amaq news agency of the local chapter of Islamic State said on the Telegram messaging app.
An AFP team was conducting an interview inside the information ministry next door when Wednesday’s blast took place.
A company driver waiting outside saw a man holding a bag and with a rifle slung over his shoulder walk past before the man blew himself up.
“He passed by my car and after a few seconds there was a loud blast,” Jamshed Karimi said, adding he saw 20 to 25 casualties. “I saw the man blowing himself up.”
Kabul police spokesman Khalid Zadran said five civilians were killed and several more wounded by the blast.
The local IS branch, known as Islamic State-Khorasan (ISK), claimed that the blast killed at least 20 people, “including several ‘diplomatic’ employees.”
Italian nongovernmental organisation Emergency NGO, which operates a hospital in Kabul, said it received more than 40 wounded people.
“Casualty numbers are continuing to rise,” Emergency said in a statement. “We have also set up beds in the kitchens and canteen.”
Bodies lay strewn on the road in the aftermath outside the high-walled compound of the ministry, marked with the Taliban flag, a video verified by AFP showed.
Some wounded people writhed on the ground, screaming for help, and a handful of onlookers scrambled to offer assistance.
The ministry itself did not appear to be badly damaged. Window panes in the interior ministry were also shattered by the explosion.
“There was supposed to be a Chinese delegation at the foreign ministry today, but we don’t know if they were present at the time of the blast,” deputy minister of information and culture Muhajer Farahi told AFP.
However, Ahmadullah Muttaqi, a senior official at the prime minister’s office, said no foreigners were present at the ministry when the suicide bomber struck.
Tom West, the US special representative on Afghanistan, tweeted that diplomats “have seen reports of at least 20 dead and many more injured. This violence serves no purpose.”