ISLAMABAD (AP) — Pakistan’s military on Wednesday said a soldier was killed and another wounded in the country’s northwest by fire from across the Afghan border, a sign of increasing violence in an area that until recent years served as a base for Pakistani and foreign militants.

The attack hit a border security post in Bajur district, a former tribal region of Khyber Pakhtunkhwa province. The military statement said the shooting came from the Afghan side of the frontier, and did not speculate on who was behind the attack.

Similar cross-border attacks in Bajur district killed two Pakistani soldiers in July and September, respectively.

Pakistan’s border areas served as a base for the Pakistani Taliban and other militants until a few years ago, when the army said it cleared the region of insurgents, but occasional attacks have continued.

Such attacks have raised fears that the Pakistani Taliban are regrouping.

Pakistan and Afghanistan often accuse each other of turning a blind eye to militants operating along the porous frontier, which stretches 2,400 kilometers (1,500 miles) across rugged mountainous terrain.

A United Nations report in July said more than 6,000 Pakistani insurgents were hiding in Afghanistan, most belonging to the Pakistani Taliban.

Also known as Tehreek-e-Taliban Pakistan, they are a separate insurgent group from the Afghan Taliban, although Pakistan’s militant groups are often interlinked with those across the border.

Pakistan’s military has been waging a decades old battle with Tehreek-e-Taliban Pakistan, some of whom have aligned themselves with the Islamic State affiliate headquartered in Afghanistan.

In September, two Pakistani soldiers were killed in a shootout with militants during a search operation in North Waziristan district, which also borders Afghanistan. Earlier that month, the Pakistani Taliban took responsibility for a powerful roadside bombing in the same district that targeted a military vehicle, killing three soldiers and wounding four.