A blast close to a secondary school in the Afghan capital Kabul has left at least 55 people dead and injured more than 150, officials have said.
The explosion took place as students were leaving the building on Saturday, with pictures on social media showing abandoned school bags in the street.
Footage on TV channel ToloNews showed chaotic scenes, with books and school bags strewn across a bloodstained road, and residents rushing to help victims.
"It was a car bomb blast that occurred in front of the school entrance," an eyewitness told Reuters, asking not to be named. He said all but seven or eight of the victims were schoolgirls going home after finishing their studies.
At the Sayed ul Shuhada high school, girls and boys study in three shifts, the second of which is for female students, Najiba Arian, spokeswoman for the Ministry of Education, told Reuters. The wounded were mostly female students, she said.
No-one has admitted carrying out the attack in Dasht-e-Barchi - an area often hit by Sunni Islamist militants.
The neighbourhood is home to many from the Hazara minority community, who are of Mongolian and Central Asian descent and are mainly Shia Muslims.
Almost exactly a year ago, a maternity unit at the local hospital was attacked, leaving 24 women, children and babies dead.
The exact target for Saturday's attack is unclear.
Reports from the city say it was busy with shoppers ahead of this year's celebrations for Eid al-Fitr next week.
Students were also streaming from the school. Najiba Arian, ministry of education spokeswoman, told Reuters news agency the government-run school was open to boys and girls.
Most of the those hurt were girls, who study in the second of three sessions, according to Arian.
Several witnesses described hearing three separate explosions, while one woman told AFP news agency she had seen "many bloodied bodies in dust and smoke".
"I saw a woman checking the bodies and calling for her daughter," the woman, Reza, said. "She then found her daughter's bloodstained purse after which she fainted and fell to the ground."
The European Union's mission in Afghanistan said on Twitter that "targeting primarily students in a girls' school, makes this an attack on the future of Afghanistan".
The attack comes against a backdrop of rising violence as the US looks to withdraw all its troops from the country by 11 September.
'Unforgivable attack'
Washington's top diplomat in Afghanistan, Ross Wilson, condemned the attack in a post on Twitter: "With scores murdered, this unforgivable attack on children is an assault on Afghanistan's future, which cannot stand."
The Taliban and United States last year signed an agreement to end the 20-year war, which started with US and allied forces invading Afghanistan following the 11 September 2001 attacks in the United States by al Qaeda, whose leader, Osama bin Laden, was being given shelter by the Taliban government.
Under the agreement, Washington was to pull out troops in exchange for Taliban security guarantees and for the group to start peace talks with the Afghan government. Talks began last year but have since stalled.
Taliban attacks on foreign forces have largely ceased, but they continue to target government forces. A number of journalists, activists and academics have also been killed in attacks blamed on the Taliban, who deny involvement.
Neighbouring Pakistan, which has considerable influence over the Taliban and is pushing them to restart peace talks and agree to a ceasefire, also condemned the attack.
Last month, Washington said it was pushing back the troop withdrawal deadline from 1 May to 11 September, which the Taliban warned could have consequences for the agreement.
- BBC / Reuters