Angry Afghan Afghans wants the government to answer how a sewage tank truck packed with explosives could penetrate a heavily fortified area of the Afghan capital and carry out the deadliest attack in Kabul since 2001, according to Radio Liberty.

They reportedly also want the government to provide some explanation for the security lapse that resulted in the deaths of at least 90 people and more than 400 wounded.

The May 31 explosion, whose casualties were mainly civilians, including women and children, occurred during the morning rush hour in the district known unofficially as the Green Zone, home to foreign embassies, NATO's headquarters, and the presidential palace

A number of Kabul residents have accused the national-unity government of a major security and intelligence blunder. 

The bombing followed a recent shakeup of security agencies, prompted by a wave of violence including the April 21 Taliban attack on a military compound in Balkh Province that killed over 140 army personnel.

The Kabul explosion occurred in Wazir Akbar Khan, considered one of the capital's safest districts. Foreign embassies are protected by dozens of 3-meter-high walls and government offices are guarded by police and security forces.

The blast was so powerful it left a 4-meter crater in front of the German Embassy.  Windows in buildings as far as 2 kilometers away were broken.

There has been no claim of responsibility, though a series of attacks in the Afghan capital over the past year have been claimed by either the Taliban or Islamic State (IS) militants.

Kabul Province had the highest number of casualties in the country in the first three months of 2017.

The blast comes amid the ongoing spring offensive by the Taliban.  Taliban militants now control or contest about 40 percent of the country, according to U.S. estimates, though Ghani's government holds all provincial centers.