Just two days ago the government blamed the Taliban for the carnage, but the insurgents denied responsibility.

The Taliban on Monday declared a three-day ceasefire across Afghanistan to mark this week's Eid Al Fitr holiday.

Just two days ago the government blamed the Taliban for the carnage, more than 50 people — mostly young girls — but the insurgents denied responsibility and issued a statement saying the nation needed to "safeguard and look after educational centres and institutions".

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The ceasefire offer comes as the United States continues to pull out its last 2,500 troops from the violence-wracked country despite faltering peace efforts between the Taliban and Afghan government to end a decades-long war.

Afghan security forces stroll in Kabul. Eid Al Fitr marks the end of the Muslim fasting month of Ramadan.

"Mujahideen of the Islamic Emirate are instructed to halt all offensive operations against the enemy countrywide from the first till the third day of Eid," a statement released by the Taliban said.

"But if the enemy conducts any assault or attack against you during these days, stand ready to robustly protect and defend yourselves and your territory," it added.

Eid Al Fitr marks the end of the Muslim fasting month of Ramadan, and the holiday begins according to the sighting of the new moon. The Taliban declared similar ceasefires last year to mark Islamic holidays.

The government usually reciprocates with a truce. Fraidon Khawzon, spokesman for chief negotiator Abdullah Abdullah, said early Monday: "We welcome the announcement....the Islamic republic is also ready and will announce soon."

Taliban chief warns US

The United States was supposed to have pulled all forces out by May 1 as agreed with the Taliban last year, but Washington pushed back the date to September 11 -- a move that angered the insurgents.

US Marines watch during the change of command in Shorab military camp in Afghanistan. File/AP

The leader of the Taliban, Hibatullah Akhundzada, reiterated in a message released ahead of Eid that any delay in withdrawing the troops was a "violation" of that deal.

"If America again fails to live up to its commitments, then the world must bear witness and hold America accountable for all the consequences," Akhundzada warned in Sunday's message.

Afghan President Ashraf Ghani has declared a day of national mourning for Tuesday.

"This savage group does not have the power to confront security forces on the battlefield, and instead targets with brutality and barbarism public facilities and the girls' school," he said in a statement.

Saturday's blasts drew widespread global condemnation.

Pope Francis called it "an inhumane action", while Iran blamed the jihadist Islamic State.

India, meanwhile, called for the dismantling of "terrorist sanctuaries" and a ceasefire to boost peace efforts.