The Taliban have largely refrained from launching major attacks in Kabul since February previous year, when they signed a deal with the United States that paved the way for peace talks and withdrawal of the remaining USA troops. An injured girl is being brought on a stretcher to a hospital.
Images circulating on social media purportedly showed bloodied school backpacks and books strewn across the street in front of the school, as smoke rose above the neighbourhood.
"They have carried out similar attacks on education institutions in the past", said Arian.
He implored residents to cooperate and allow ambulances free access to the site.
"I rushed to the scene (after the blasts) and found myself in the middle of bodies, their hands and heads cut off and bones smashed", said Mohammad Taqi, a resident of Dasht-e-Barchi, whose two daughters were students at the school but had escaped the attack.
The radical Sunni Muslim group has declared war on Afghanistan's minority Shia Muslims.
Outside the Muhammad Ali Jinnah Hospital, in the Dasht-e-Barchi neighborhood dozens of people lined up to donate blood, while family members checked casualty posted lists on the walls.
Nearly exactly a year ago, a maternity unit at the local hospital was attacked, leaving 24 women, children and babies dead.
Both Arian and Nazari said that at least 50 people were also wounded and that the casualty toll could rise.
Residents were out shopping ahead of this week's Eid al-Fitr, which marks the end of Ramadan, the Muslim holy month of fasting.
UK PM Boris Johnson's party win election for parliament seat
Labour fielded a former Remain supporter as its candidate in a town where nearly 70 per cent backed Brexit in the 2016 referendum. In contrast, only 20 per cent of Hartlepool voters surveyed had a favourable opinion of Labour leader Sir Keir Starmer .
Taliban spokesman Zabihullah Mujahid told reporters in a message that only the Daesh group could be responsible for such a heinous crime. ISIS is not very strong in Afghanistan.
In a statement, the Foreign Office spokesperson said the Government and the people of Pakistan offer heartfelt condolences to the Government and the people of Afghanistan and pray for quick recovery of the injured.
The Taliban and the Afghan government have traded accusations over a series of targeted killings of civil society workers, journalists and Afghan professionals. A spokesman for the Taliban insurgent group denied involvement, saying they condemn any attacks against Afghan civilians.
On Saturday, President Ashraf Ghan blamed Taliban for the blast.
On Oct 24, a suicide bomber blew himself up at a tuition centre in the same district, killing 18 people in an attack that also went unclaimed.
Earlier the group took responsibility for the targeted killing of three female media personnel in eastern Afghanistan.
The attack comes days after the remaining 2500 to 3500 American troops officially began leaving the country.
But the group has clashed in near daily battles in the rugged countryside with Afghan forces even as the USA military continues its withdrawal.
The United States was supposed to have pulled all forces out by May 1 under a deal struck with the Taliban a year ago, but Washington pushed back the date to September 11 - a move that angered the insurgents.