At least four children were among five killed on Wednesday when a suspected suicide bomber targeted a school bus for a military-run institution in southwestern Pakistan, officials said.
"A bus carrying children of the APS (Army Public School) was targeted with a bomb, the nature of which is still being determined," Yasir Iqbal Dashti, a senior local government official in Khuzdar district of Balochistan province, told AFP.
"The initial probe suggests it was a suicide bombing," he added.
A senior police official confirmed the death toll to AFP on condition of anonymity, as he was not authorized to speak to the media, adding that the toll could rise.
The military, meanwhile, put the death toll at five, including four children, in a statement to the media.
The school caters to the children of army personnel and civilians living in the area.
Images shared on social media showed the shattered remains of a school bus, its windows broken, and a pile of school bags placed near the scene.
In a statement, Prime Minister Shehbaz Sharif offered his "sympathies" to the families of the children who fell victim to "brutality."
Sharif also accused archrival India of backing militants, which Islamabad routinely accuses of fomenting militancy in Pakistan by supporting proxies, including Baloch separatists, who have intensified attacks in recent years.
"Terrorists operating under Indian patronage attacking innocent children on a school bus is clear evidence of their hostility," the statement added.
The military in a statement also said Wednesday's attack was "planned and orchestrated" by India.
No group has yet claimed responsibility for the bombing, which comes weeks after nuclear-armed neighbors reached a cease-fire to end their most serious conflict in decades.
The Baloch Liberation Army (BLA) is the most active group in the region and often carries out deadly attacks against security forces, but the local chapter of the Daesh terrorist group, as well as the Pakistani Taliban, has also claimed recent attacks.
In March, dozens of militants and off-duty security force members died when the BLA took control of a train with hundreds of passengers on board.
In 2014, the Army Public School in Peshawar in northwestern Khyber Pakhtunkhwa province was attacked by gunmen who killed more than 150 people, mostly students.
The horrific attack sparked a massive crackdown against militancy that had thrived for years in the border regions.
