The ammonium nitrate was stuffed in 20 bags sent by the Taliban-allied Haqqani network from neighbouring Pakistan, the National Directorate of Security (NDS) said.
The material was discovered during an official raid on a Kabul neighbourhood on Monday, two days after Taliban insurgents attacked a Spanish embassy compound in the Afghan capital.
"This amount of explosive material is enough for four or five powerful car bombs or hundreds of smaller bombs," an Afghan official told AFP, requesting anonymity.
Afghanistan has repeatedly accused Pakistan of nurturing the Taliban on its soil, even as President Ashraf Ghani has sought to repair strained bilateral ties in the hope of reviving peace talks with the insurgents.
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The Haqqani network, a hardline group linked to the Taliban, has been blamed for some of the deadliest attacks in Kabul and other Afghan cities in recent years.
The Taliban, overthrown from power in 2001, have stepped up attacks on government and foreign targets in recent months despite Ghani's peace overtures.
At least six people, including two Spaniards, were killed in the latest attack in Kabul's high-security diplomatic quarter, which lasted for around 10 hours.