A tanker truck believed to be carrying either water or human waste exploded on Wednesday near Zanbaq Square in Kabul's 10th district, close to shops and restaurants as well as government offices and foreign embassies.
There was no immediate claim of responsibility. Zabihullah Mujahid, a spokesman for the Taliban, told Al Jazeera that the group was not involved in the attack.
Police and health officials confirmed to Al Jazeera that at least 80 people were killed and more than 300 wounded in the attack.
Reporting from Kabul, Al Jazeera's Qais Azimy cited sources as saying that the death toll could be as high as 100, with more than 500 wounded.
"This is one of the biggest attacks in Afghanistan that I have ever seen," he said. "It's a very sad and very bloody day for the people of Kabul."
Aziz Navin, an IT engineer with the Afghan TOLOnews outlet, was one of the first victims to be named.
Mohammed Nazi, a driver with the BBC, was also killed while four journalists from the British public broadcaster were being treated in hospital.
"[Nazir] was driving journalist colleagues to the office," the BBC said in a statement posted to Twitter. "He was in his late thirties and leaves a young family."
An Afghan security guard at the German embassy also died in the attack.
The victims appear mainly to have been Afghan civilians, and there were no immediate reports of casualties among foreign embassy staff.
"The area is heavily guarded, and there is usually traffic jam, just because of security-controlled points in the area," Mushtaq Rahim, an independent analyst and security commentator, told Al Jazeera from Kabul.
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