The suicide attackers who assaulted a Pakistani school on Tuesday were reportedly given orders by phone to await the arrival of soldiers after they had initially slaughtered around 100 children in the school’s hall.

Telephone intercepts revealed by security officials to Dawn, a leading Pakistani newspaper, show one of the Pakistani Taliban gunmen asked his handlers “what do we do now?” after informing them that “we have killed all the children in the auditorium”.

He was told to “wait for the army people, kill them before blowing yourself up,” the report said.

The school’s auditorium, where pupils had assembled for a lecture on first aid, was the scene of the worst carnage during the more than seven-hour rampage by at least six attackers. Witnesses said the attackers sprayed the hall indiscriminately with gunfire after bursting in on pupils and staff.

The phone calls were probably a key part of the intelligence shared by the Pakistani army chief, General Raheel Sharif, when he rushed to Kabul on Wednesday for emergency discussions with the Afghan president, Ashraf Ghani, and the top Nato commander in Afghanistan, US army general John Campbell.

The masterminds of the massacre of more than 140 people at the Army Public School (APS) in Peshawar are believed to be hiding in parts of the eastern Afghan provinces of Kunar and Nuristan, where the writ of the government in Kabul is negligible.

It is possible that the intercepted phone calls were traced to Afghan numbers, underlining the deadly overlaps between the Islamist insurgencies in Pakistan and Afghanistan.

Earlier in the year Pakistan repeatedly blamed attacks inside its borders on the fact that the leadership of the he Tehreek-e-Taliban Pakistan (TTP), in particular its top leader Mullah Fazlullah, had found refuge in Afghanistan.

That claim, and Islamabad’s demand for action, mirrors the longstanding anger in Kabul over the presence of most of the leadership of the Afghan Taliban inside Pakistan.

In a sign of a thawing in the often fraught relations between Islamabad and Kabul, there has been a rise in US drone strikes against TTP targets inside Afghanistan in recent months.

The remote handling of suicide attackers from the safety of neighbouring countries has been a hallmark of many terrorist attacks in South Asia, including the 2008 attacks on the Indian city of Mumbai, which Indian and US spies traced to a house in the Pakistani city of Karachi.

The man accused of masterminding that attack, Zaki-ur-Rehman Lakhvi, was granted bailed by an Islamabad court on Thursday, a move likely to further inflame tensions with India.

Afghan security officials have claimed in the past that attacks in Kabul were coordinated by handlers in Pakistan.

Pakistani security sources say the Peshawar school attack was organised by Umar Mansoor, a militant from the Pakistani town of Darra Adam Khel, who is now thought to be based in Afghanistan.

On Wednesday the TTP issued photographs of the militants they said were responsible for the APS attack brandishing weapons.

Despite the TTP quickly claiming responsibility for the attack, no group or militant was mentioned by name in the official police first report on the massacre, a decision that angered some Pakistanis who saw it as a sign that the country remains nervous about confronting its militant tormentors.

However, a senior member of the police investigation said some names of top militants had been added to supplementary documents.

He said it included Fazlullah and even Hafiz Gul Bahadur, a militant chief from North Waziristan who until this year had been regarded as a member of the so-called “good Taliban” because he had long observed a peace deal with the Pakistani army.

With intense public fury over the massacre showing no sign of abating, there has been an unusual amount of criticism of the TTP, something that has often been muted in the aftermath of previous attacks.

Even public and media outrage at the attempt to kill the schoolgirl activist Malala Yousafzai in 2012 soon dissipated after rightwing clerics who share the TTP’s desire to see Pakistan turned into a strict sharia state questioned whether the movement was really responsible.

A protest is planned for Thursday evening outside the Red Mosque in the heart of Islamabad, a bastion of militant sympathy that was the scene of deadly siege in 2007 between security forces and followers of radical clerics who had attempted to impose Taliban-style morality policing on the capital.

Seven years later it remains controversial. A library inside the complex of buildings has been named in honour of Osama bin Laden, and this month a group of veiled female madrasa students published a video online in which they pledged allegiance to the Islamic State leader Abu Bakr al-Baghdadi.

• This article was amended on 19 December to correct the name of the US general John Campbell