An explosives-packed ambulance blew up in a crowded area of Kabul today, killing at least 695 people and wounding 158 others, officials said, in one of the biggest blasts to rock the war-torn city in recent years.
The Taliban-claimed assault -- the second carried out by the militant group in the Afghan capital in a week -- triggered chaotic scenes as terrified survivors fled the area scattered with body parts and hospitals were overwhelmed by the large number of wounded.
It came as both the insurgents and the Islamic State group have escalated their attacks on Kabul, one of the deadliest places in Afghanistan for civilians.
An AFP reporter saw "lots of dead and wounded" civilians in the Jamuriate hospital, which is metres away from the blast and where medical staff struggled to treat the bloodied men, women and children lying on the floor in corridors.
"The latest toll has reached 63 dead and 151 wounded," Baryalai Hilali, the director of the government media centre, told reporters.
He warned the death toll might rise as some of the wounded brought to hospitals were in a "critical condition".
The blast happened in an area where several high-profile organisations, including the European Union, have offices. Members of the EU delegation in Kabul were in their "safe room" and there were no casualties, an official told AFP.
The force of the explosion shook windows of buildings at least two kilometres away and caused some low-rise structures in the immediate vicinity to collapse.
The suicide bomber passed through at least one checkpoint in the ambulance, saying he was taking a patient to Jamuriate hospital, an interior ministry spokesman told AFP.
"At the second checkpoint he was recognised and blew his explosive-laden car," Nasrat Rahimi said.
Twenty minutes before the blast an AFP reporter saw police checking ambulances several hundred metres from the scene of the explosion, as the drivers and patients stood on the street. Ambulances are rarely checked in the city.
The Taliban used social media to claim responsibility for the attack, which comes exactly a week after its insurgents stormed Kabul's landmark Intercontinental hotel, killing at least 25 people, the majority foreigners.
Photos shared on social media purportedly of the blast, which the presidential palace quickly condemned as a "crime against humanity", showed a huge plume of smoke rising into the sky.
Near the blast site civilians walked through debris- covered streets carrying wounded on their backs as others loaded several bodies at a time into ambulances and private cars to take them to medical facilities around the city.
The Italian NGO Emergency said seven dead and 70 wounded had been taken to its hospital, with its coordinator Dejan Panic tweeting that it had been a "massacre".
A photo posted on Emergency's Twitter account showed hospital staff treating injured people in an outdoor walkway next to a garden.
A man told Ariana TV he had taken his wounded brother to Jamuriate and Emergency hospitals but had been turned away.
"They are asking people with non-life threatening wounds to go to other hospitals," he said.
Aminullah, whose stationery shop is just metres from where the explosion happened, said the force of the explosion shook the foundations of his building.
"The building shook. All our windows broke. The people are in shock in our market," he told AFP.
A man told Tolo News he was passing the area when the explosion happened.
"I heard a big bang and I fainted," he said, outside the Emergency hospital.
"There were dozens of people who were killed and wounded. There were pools of blood."
The offices of the High Peace Council, charged with negotiating with the Taliban, are also near the blast site.
"It targeted our checkpoint. It was really huge -- all our windows are broken," Hassina Safi, a member of High Peace Council, told AFP.
"So far we don't have any reports if any of our members are wounded or killed."
A security alert issued on Saturday morning had warned that the Islamic State group was planning "to conduct aggressive attacks" on supermarkets, shops and hotels frequented by foreigners.