Hekmatyar's stomping grounds include Kunar province, a sweep of heavily forested mountains in eastern Afghanistan.

NPR: For Afghan Fighter the War Continues as Loyalties Shift

It is unclear how many foot soldiers Messrs Omar and Hekmatyar have, or how determined they are.

ECONOMIST: Enter the suicide bomber

He says after the Soviets left in 1989, Hekmatyar's career took a twist.

NPR: For Afghan Fighter the War Continues as Loyalties Shift

These days, the US State Department lists Gulbuddin Hekmatyar as an international terrorist.

NPR: For Afghan Fighter the War Continues as Loyalties Shift

But only a couple of decades ago, Hekmatyar was the largest recipient of CIA-supplied arms and money channeled through Pakistan's intelligence services.

NPR: For Afghan Fighter the War Continues as Loyalties Shift

While most attacks in the Afghan war are carried out by the Taliban, the explosion on Thursday was claimed by Hezb-e-Islami, a smaller insurgent group led by warlord Gulbuddin Hekmatyar.

WSJ: Deadly Blast Hits Afghan Capital