"There was blood everywhere, all over the room, so scary and awful", he said.
The Ghazni attack, one of the Taliban's most devastating in years, has left questions over hopes for peace talks aroused by an unprecedented ceasefire during the Eid celebration in June and a meeting last month between Taliban officials and a senior U.S. diplomat.
"What is this national security council really doing, the security council is supposed to sit and observe, these issues must be discussed in the security meetings and cabinet meetings", said General Sikandar Asghari, a former deputy head of the Afghan Local Police directorate.
"What's crystal clear is that almost four years after the Afghan security forces took over the war efforts, they're still woefully unprepared for the task despite very real improvements in capacities in recent years".
"U.S. airpower has killed more than 220 Taliban since August 10", O'Donnell said.
The UNs special envoy to Afghanistan, Tadamichi Yamamoto, said: "Reports indicate that the death toll in Ghazni is high, including government forces, Taliban fighters and civilians".
Abdul Hai Nemati, the governor of Baghlan, said at least nine security forces were still missing and four others were wounded in the attack.
There was no immediate word of a claim of responsibility, but Taliban spokesman Zabiullah Mojahid denied that the group was to blame.
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An Afghan official says Taliban attacks have killed four police in southern Zabul province.
Nahida Rahimi, a doctor at Kabul's Isteqlal Hospital, where some of the wounded are being treated, said a mother told her she had lost a son in Wednesday's bombing after already losing another a year earlier in another suicide bombing, also in Kabul, that targeted Shiites.
A man who was injured in a deadly suicide bombing that targeted a training class in a private building in the Shiite neighbourhood of Dasht-i Barcha, is placed in an ambulance in western Kabul, Afghanistan, Wednesday, Aug. 15, 2018.
Meanwhile, a Taliban assault on two adjacent checkpoints in northern Afghanistan late on Tuesday night killed at least 30 soldiers and policemen, officials said. Dilawar Aymaq, a parliamentarian from Baghlan, confirmed the attack.
Afghanistan has seen a recent upsurge in militant violence, including a major Taliban assault on the eastern city of Ghazni.
Ghazni residents who arrived in Kabul after fleeing the violence told AFP that the dead bodies of militants and soldiers continued to litter the streets, while government offices have been set ablaze by Taliban fighters and food prices are rising.
"The extreme human suffering caused by the fighting in Ghazni highlights the urgent need for the war in Afghanistan to end", the top United Nations official in Afghanistan, Tadamichi Yamamoto, said in a statement.
He said a gun battle lasted several hours, during which the Taliban used artillery and heavy guns.
The fall of a northern base this week, with at least 17 soldiers killed, was a further blow to Afghan security forces, already demoralised by staggering casualties.