Three children were among five people killed in a school bus bombing on Wednesday in Pakistan's Balochistan province that Islamabad quickly blamed on Indian proxy militants.
The south-western province has been plagued by a decades-long separatist insurgency orchestrated by armed groups, which Pakistan says are backed by New Delhi.
A suicide bomber is believed to have attacked the bus, which was carrying pupils to a military-run school, Pakistan's army said. More than 30 people were also wounded. Officials said the death toll could rise because several children were in critical condition.
"The initial probe suggests it was a suicide bombing," Yasir Iqbal Dashti, a senior official in Balochistan's Khuzdar district, told news agency AFP. About 40 pupils were on the bus when it was bombed, he said.
Images shared on social media showed the shattered remains of the bus, its windows broken and school bags piled up near the scene.
Prime Minister Shehbaz Sharif accused arch-rival India of involvement and offered his sympathy to the families of the children.
Mr Sharif said New Delhi has been backing Baloch separatists.
"Terrorists operating under Indian patronage attacking innocent children on a school bus is clear evidence of their hostility," Mr Sharif said.
The Pakistani military also said the attack was "planned and orchestrated" by India. There was no immediate comment from New Delhi but it has previously denied claims it supports militancy.
Pakistan’s Interior Minister Mohsin Naqvi condemned the attack and called the perpetrators “beasts” who deserve no leniency, saying it was an act of “sheer barbarism”.
No group has yet claimed responsibility for the bombing, which comes weeks after nuclear-armed Pakistan and India reached a ceasefire to end their most serious conflict in decades. Cross-border fighting broke out earlier this month over the disputed Himalayan region of Kashmir, which is divided between the two nations but sought in its entirety by both.
A ceasefire was reached on May 10 but the exchange of fire raised fears of a broader war.
The Baloch Liberation Army is the most active militant group in Balochistan and often carries out deadly attacks against Pakistani security forces. The local chapter of ISIS as well as the Pakistani Taliban have also claimed attacks. During the recent Kashmir hostilities, the Baloch Liberation Army appealed to India for support. New Delhi has not commented on the appeal.
In March, the Baloch Liberation Army took control of a train with hundreds of passengers on board in a hijacking that killed dozens of militants and off-duty security force personnel.
In 2014, another military-run school, in Peshawar in the north-western province of Khyber Pakhtunkhwa, was attacked by gunmen who killed more than 150 people - mostly pupils. The assault was claimed by the Tehreek-e-Taliban Pakistan, an ultra-radical Islamist group. The incident sparked a major crackdown on militancy in border regions.
Though it is Pakistan’s largest province, Balochistan is its least populated. It is a hub for the country’s ethnic Baloch minority, who say they face discrimination. The region of about 15 million people is home to key mining projects, but many locals say they are not reaping the economic benefits.
Earlier this week, the Baloch Liberation Army vowed more attacks on the “Pakistani army and its collaborators” and said its goal is to "lay the foundation for a peaceful, prosperous and independent Balochistan”.
