The Afghan health ministry says 158 people were wounded in the attack
At least 95 people have been killed and 158 injured after a suicide bomb attack in the Afghan capital of Kabul.
Interior ministry deputy spokesman Nasrat Rahimi said the bomber had used the ambulance to pass through one checkpoint, saying he was taking a patient to a nearby hospital.
When he reached the second checkpoint, he was recognised and blew up the vehicle.
Police had identified the car bomb before the detonation but had hoped to push it away from the crowd when the suicide bomber detonated the explosives, according to Afghan news network Ariana.
Among the buildings in the area are the High Peace Council and Kabul's police headquarters. The European Union also has an office nearby.
Hassina Safi, a member of High Peace Council, which is charged with negotiating with the Taliban, told AFP: "It targeted our checkpoint.
"It was really huge - all our windows are broken.
"So far we don't have any reports if any of our members are wounded or killed."
Witnesses reported that the blast shattered windows of surrounding buildings and caused some smaller buildings to collapse.
The Jamuriate hospital, the nearest to the scene, was overwhelmed, with many people lying in corridors waiting to be treated.
Outside the hospital, people were carrying the injured on their backs and paramedics loaded several people into ambulances at once.
The Taliban has claimed it is behind the attack.
It comes just days after 22 people were killed during a 17-hour siege of Kabul's Intercontinental Hotel and an attack on the offices of Save The Children in the eastern city of Jalalabad.
Dr Abdullah Abdullah, chief executive of the Islamic Republic of Afghanistan, wrote on Twitter that Saturday's attack was "insane, inhuman, heinous and a war crime."
Terrorist attack on civilians & hospital in #Kabul is insane, inhuman, heinous and a warcrime. We will bring its perpetrators to justice & take necessary measures to avoid such barbarism in the future. Int Community must take further action against state sponsored terrorism.— Dr. Abdullah (@afgexecutive) January 27, 2018
He added: "We condemn this terrorist act and share the sorrows and loses of our people.
"Our priority and focus right now is to help those in need and provide the best treatment for those wounded.
"This is the moment when we all need to stand together and punch our enemy hard. This is enough!"
We condemn this terrorist act and share the sorrows and loses of our people. Our priority and focus right now is to help those in need and provide the best treatment for those wounded. This is the moment when we all need to stand together and punch our enemy hard. This is enough!— Dr. Abdullah (@afgexecutive) January 27, 2018