In the first 10 months of a year ago alone, some 6,785 soldiers and police were killed.
USA advisers say that Afghan security forces, fighting largely alone since a NATO-led coalition ended its main combat mission in 2014, have made progress but still rely too much on vulnerable checkpoints exposed to Taliban attack.
The Taliban have claimed responsibility for the horrific attack in the Afghan capital.
Several prominent political leaders, such as Hazara leader Mohammad Mohaqiq, live in western Kabul.
The explosives, weighting 2,500 kilograms of ammonium nitrate, had skillfully been placed in 50 bags in the truck for suicide attacks in the capital, the intelligence agency said.
Kabul has been battered by explosions claimed by the Taliban and by the Islamic State group's affiliate in Afghanistan.
The Interior Ministry in a statement called the attack a "criminal attack against humanity".
A spokesman of the Afghanistan Ministry of Defence said today that the militants attacked an army camp in Khakrez district of Kandahar province.
"The police are corrupt, the security people are corrupt and the people are against the government, all this together makes it easy for the Taliban", said Wahidi.
The Taliban were reportedly engaged in fighting with security forces in the northern province of Baghlan, temporarily closing a key highway between the capital, Kabul, and northern Afghanistan. Taliban spokesman Mujahid claimed the bus was filled with employees of the intelligence services saying 37 people were killed, but the Taliban often exaggerate their battlefield gains and death tolls.
USA military officials maintain Taliban insurgents and their dreaded ally, the Haqqani network, are using sanctuaries on Pakistani soil to sustain the Afghan insurgency. Apart from inflicting casualties on the struggling Afghan security forces, they also seized the outpost and captured weapons and vehicles.