Both the Taliban and the Islamic State group have stepped up their attacks in Kabul since 2016, turning the city of some five million people into the one of the deadliest places in Afghanistan for civilians.
Here are some of the key moments in the security of the Afghan capital over the last two years.
First Islamic State attack
After carrying out multiple attacks across Afghanistan, IS claimed its first assault in Kabul in July 2016 as twin explosions ripped through crowds of Shiite ethnic Hazaras, killing at least 85 people and wounding more than 400.
Since then IS has escalated its presence in the city, claiming nearly 20 attacks across Kabul in the past 18 months, and establishing cells including students, professors and shopkeepers evading Afghan and US security forces.
The group's attack on Hazaras was the deadliest in Kabul in 2016, which brought new levels of carnage even to a city already grimly accustomed to atrocities.
Other attacks included a truck bomb and ensuing firefight that killed at least 64 people and wounded some 350 others on April 19, a week after the start of the Taliban's "spring offensive".
And Taliban militants launched an assault on the Kabul offices of CARE International, part of a wave of bombings in the city on September 5 that left at least 41 people dead and dozens wounded.
The truck bomb
A massive truck bomb on May 31, 2017 killed more than 150 people and wounded hundreds in the city's fortified diplomatic quarter, the deadliest attack in Kabul since the US invasion began in late 2001.
The bomb, which no group has claimed responsibility for, prompted authorities to develop a new plan to expand their ring of steel around the city and impose tight restrictions on large vehicles.
But the time consuming checks result in hundreds of trucks waiting hours before they can proceed, and officials are forced to acknowledge that with more than a hundred ways in to Kabul it is impossible to control all the entrances.
Their point is proven just months later, when a suicide bomber on foot evades checkpoints to reach the "Green Zone" and blow himself up, killing at least five people and wounding dozens.
Saturday's attack was another chilling demonstration of the militants' ability to evade security and penetrate the heart of the city.
Bloody end to 2017
The truck bomb was not the only notable Kabul attack of 2017. Among many smaller assaults which killed dozens of people were an attack on Afghanistan's largest military hospital in March which officially left at least 50 people dead, though security sources and survivors say the toll exceeded 100.
Minority Shiites increasingly became targets as Sunni IS stepped up their assaults, with dozens killed in multiple attacks. The deadliest -- in which some 40 people were killed and dozens wounded -- was one of three assaults claimed by the Middle Eastern jihadist group in December alone.
The parliament, the Supreme Court, and security installations as well as foreign forces in Kabul also came under attack in 2017, with civilians paying a disproportionate price.
US President Donald Trump also announced his new strategy for Afghanistan in 2017, vowing in August that troops would stay there indefinitely. The Taliban responded with a wave of attacks across the country.
No end in sight
Just four days into 2018 another suicide blast rocked Kabul, in an Islamic State-claimed attack which killed at least 13 people.
Then the Taliban stormed the landmark Intercontinental Hotel in a complex assault in which witnesses told AFP the gunmen went from room to room targeting foreigners for nearly 12 hours before being killed by Afghan security forces.
Despite heightened threats in Kabul, visitors to the hotel described lax security ahead of the attack, which began late on January 20.
It was the start of another bloody week across the country, with an IS attack on a Save the Children compound in eastern Jalalabad city killing at least five people and forcing the charity to suspend operations.
More security alerts were issued in Kabul early Saturday, warning of attacks targeting places frequented by foreigners.
Twenty minutes before Saturday's blast an AFP reporter saw police checking ambulances several hundred metres from the scene of the explosion.
Ambulances -- ubiquitous at the site of the dozens of attacks that rock Kabul each year -- are rarely checked in the city.
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