A suicide bomber blew himself up near Afghanistan's foreign ministry where a Chinese delegation had been due to meet on Wednesday, causing more than 20 casualties, Taliban officials and witnesses said.

The Taliban claim to have improved security since storming back to power in 2021 but there have been scores of bomb blasts and attacks, many claimed by the local chapter of the Islamic State (IS) group.

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 with a backpack and 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.

"I saw the man blowing himself up."

Kabul police spokesman Khalid Zadran confirmed the blast "which unfortunately resulted in casualties".

"Security teams have reached the area," he tweeted.

In the aftermath, bodies lay strewn on the road outside the high-walled compound of the ministry, marked with the Taliban flag, a video verified by AFP showed.

Some injured 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.

"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.

At least five Chinese nationals were wounded last month when gunmen stormed a hotel popular with Chinese business people in Kabul.

That raid was claimed by IS, who also took responsibility for an attack on Pakistan's embassy in Kabul in December that Islamabad denounced as an "assassination attempt" against their ambassador.

Four people were killed and 25 wounded in an attack on a mosque in the grounds of the interior ministry in Kabul in October, with survivors reporting it was a suicide bombing.

And two Russian embassy staff members were killed in a suicide bombing outside their mission in September in another attack claimed by IS.

Hundreds of people, including members of Afghanistan's minority communities, have been killed and wounded in other attacks since the Taliban regained power.

Afghanistan's regional chapter of the Islamic State group is known as Islamic State-Khorasan (IS-K), a historical term describing the vast territory they hope to rule spanning India, Iran and Central Asia.

The Taliban and IS-K share an austere Sunni Islamist ideology but the latter are crusading to establish a global "caliphate" instead of the Taliban's more modest and inward-looking goal of ruling an independent Afghanistan.