ISLAMABAD, Pakistan — A powerful explosion hit a Pakistani Army convoy early Thursday in the North Waziristan tribal region, killing at least nine soldiers while leaving several others critically injured, according to a Pakistani security official based in the area.

The official, who spoke on the condition of anonymity, said the army convoy came under attack while carrying troops to a checkpoint near the border with Afghanistan. The explosion also damaged several vehicles.

North Waziristan, one of seven tribal districts of Pakistan’s semiautonomous tribal region near the Afghan border, is the base for myriad Taliban factions and has been home to Al Qaeda for many years, although as of Thursday evening, no group had claimed responsibility for the blast.

Soon after the blast, security forces cordoned off the surrounding area in a search for the attackers. Army helicopters also went after militants’ hide-outs in the area, although no casualties were reported in the aerial attack.