In a statement issued by the US State Department, Washington called the attack “barbarous” and called for the immediate end to violence.
Early Sunday, reports indicated that the death toll had risen to 58 with over 150 people wounded.
The incident happened on Saturday evening when a car bomb was detonated close to the school. Among the victims are many students, including girls.
In their statement, the US said: “The United States condemns the barbarous attack near a girls’ school in Kabul, Afghanistan.”
The State Department also said that the US will continue to support and partner with people of Afghanistan.
“We will continue to support and partner with the people of Afghanistan, who are determined to see to it that the gains of the past two decades aren’t erased.”
According to the Afghan Ministry of Interior, three explosions took place close to the school. The first was a car bomb followed by two IEDs.
No group or individual have so far claimed responsibility for the explosions but the Taliban denied involvement in the attack in a tweet posted shortly after the incident.
However, President Ashraf Ghani has blamed the Taliban for the attack.
The UN Secretary-General Antonio Guterres has also strongly condemned the “horrific attack”.
He said those responsible for “this heinous crime” must be held accountable.
Guterres also underlined the urgency of ending the violence in Afghanistan and achieving a peaceful settlement of the conflict.
Alison Blake, the UK’s Ambassador to Kabul also condemned the attack and said: “Children must never be the target of violence.”
“Our sympathies and deepest condolences to the families and all affected by this atrocious attack on schoolchildren in Kabul.
“Words are not enough. Those responsible must be brought to justice and held to account,” she said.
The German Embassy in Kabul also issued a statement and said: “We condemn yesterday’s horrific attack on Sayed-ul-Shuhada girls high school. Killing children is an assault on the future of Afghanistan.
“Our thoughts are with victims of this despicable act and their families. Our deepest condolences to families and friends of the murdered students.”
UNICEF Executive Director Henrietta Fore also issued a statement and said violence around schools is not acceptable.
“Schools should be a place of peace and a place where children can play, learn and socialize with a sense of security and safety,” she said.
“Children should never and under no circumstances be the target of violence.
“UNICEF urges the warring parties to abide by international human rights and humanitarian law and to ensure the safety and security of all children,” Fore said.
A senior security official meanwhile told Reuters on Sunday on condition of anonymity that most of the casualties were students coming out of the Sayed ul Shuhada school, and many were badly wounded in hospital.