A suicide car bomber struck a school bus in restive southwestern Pakistan on Wednesday, killing at least four children and wounding 38 others.

Axar.az reports, citing ABC News, a local deputy commissioner, Yasir Iqbal, said the attack occurred in Khuzdar, a district in Balochistan province, as the bus was transporting children to school in the city.

No group immediately claimed responsibility, though suspicion is likely to fall on ethnic Baloch separatists, who frequently target security forces and civilians in the region.

Pakistan’s Interior Minister Mohsin Naqvi strongly condemned the attack and expressed deep sorrow over the children’s deaths. He called the perpetrators “beasts” who deserve no leniency, saying the enemy had committed an act of “sheer barbarism by targeting innocent children.”