At least three children were among five people killed when a suicide bomber targeted an army school bus in Pakistan’s restive Balochistan province, the military said on Wednesday, in an attack Pakistan blamed on Indian proxies.

Around 40 students were on the bus that was headed to an army-run school and several have sustained injuries, said Yasir Iqbal, the administrator of Khuzdar district, where the incident took place.

Pakistan’s military and Prime Minister Shehbaz Sharif swiftly released statements condemning the violence and accusing “Indian terror proxies” of involvement in the attack. They did not share evidence linking the attack to New Delhi.

India’s government did not immediately respond to a request for comment.

At least three children and two adults were killed in the attack, the army said in a statement.

Tensions between the nuclear-armed neighbours are high after they struck a ceasefire on May 10 that diplomats have warned is fragile, following the most intense military action in decades in a conflict analysts and officials feared could spiral out of control.

Both countries accuse the other of supporting militancy on each other’s soil - a charge both capitals deny. The latest military escalation, in which the two countries traded missiles, was sparked after India accused Pakistan of supporting militants who attacked dozens of tourists in the Indian portion of the contested region of Kashmir. Islamabad denies any involvement.

Southwestern Balochistan is Pakistan’s largest province by area, but smallest by population. The province of some 15 million people in the southwest of the country is home to key mining projects but has been roiled by a decades-old insurgency.

No group immediately claimed responsibility for the blast, which was reminiscent of one of the deadliest militant attacks in Pakistan’s history when an attack on a military school in the northern city of Peshawar in 2014 killed more than 130 children.

It was claimed by the Tehreek-e-Taliban Pakistan, an ultra-radical Islamist group.

Attacks by separatist groups in Balochistan have risen in recent years. The Baloch Liberation Army, a separatist militant group, blew up a railway track and took passengers from a train hostage in March, killing 31.