PAKISTAN - Pakistan observed a day of national mourning Thursday for the 21 people killed when heavily armed gunmen stormed a university in the troubled northwest, exposing the failings in a national crackdown on extremism.
Flags will fly at half-mast on all government buildings inside and outside the country, Prime Minister Nawaz Sharif's office said, while a prayer ceremony will be held in the capital Islamabad.
Sharif has vowed a "ruthless" response to the massacre and ordered security forces to hunt those behind Wednesday's attack on the Bacha Khan university in Charsadda, where students were targeted with grenades and automatic weapons.
The assault bore a chilling resemblance to a 2014 massacre at a school in nearby Peshawar which shocked the nation and prompted an escalation of a national crackdown on extremism.
Security forces killed all four gunmen in the university attack, which was claimed by a Pakistani Taliban faction but branded "un-Islamic" by the umbrella group's leadership, who also vowed to hunt down those responsible.
Among those who died was assistant chemistry professor Syed Hamid Husain who was lauded for challenging the gunmen and firing at them with his pistol while his terrified students raced for cover.
The majority of victims were laid to rest late Wednesday according to Muslim tradition, including Husain who was buried in his home village of Swabi as those who knew him paid tribute.
"He would always help the students and he was the one who knew all their secrets because they would share all their problems with him," 22-year-old geology student Waqar Ali told AFP. "He was referred to by students as 'The Protector'." The majority of the student victims died at a hostel for young men where security forces also cornered the four attackers.
Pools of blood and overturned furniture could be seen inside the hostel, while in a back alley outside, an old wooden plaque on the wall proclaimed: "Heroes die young".
Meanwhile the bodies of militants, bloodied and with their clothes torn, were unceremoniously dumped on the floor of a truck before being taken away from the scene.
The assault brought memories rushing back of the 2014 atrocity, in which gunmen from the same Taliban faction slaughtered more than 150 people at an army-run school in Peshawar on December 16 that year.
The majority of those victims were children, and their relatives held a candlelight vigil in Peshawar late Wednesday for those slain in the latest attack.
The strike on the army school united Pakistanis, already scarred by a decade of assaults, in shock and outrage and prompted a government and military-led crackdown on extremism.
Security palpably improved in 2015, which saw the least number of deaths from militant violence since the formation of the Pakistani Taliban in 2007 - but critics have repeatedly warned the government is not taking long-term steps to tackle the underlying scourge of extremism.
"We understand their pain," Ajun Khan, who lost his only son Asfand in the attack on the Army Public School, told AFP of the survivors of Wednesday's assault.
"We are not safe, even parents do not feel safe," he said.
The Bacha Khan attack, which Amnesty International said could be branded a war crime, earned global condemnation including from UN Secretary-General Ban Ki-moon and neighbouring India.
"It is particularly appalling that these terrorists continue to attack educational institutions, targeting Pakistan's future generations," said a US State department spokesman.
Sharif said in a statement from Switzerland, where he is attending the Davos forum, that he was "personally monitoring" the situation.
"The countless sacrifices made by our countrymen will not go in vain Inshallah," he said. "The entire nation is united and one against terrorism."