PESHAWAR, Pakistan (AP) — A paramilitary post in northwestern Pakistan came under attack on Monday when a drone loaded with explosives wounded several officers, according to police and local officials.

The attackers later ambushed two ambulances being used to transport the wounded, killing three officers and wounding two rescuers.

The assault took place in Karak, a district in Khyber Pakhtunkhwa province bordering Afghanistan, district police spokesman Shaukat Khan said. A search is underway for the attackers.

No group immediately claimed responsibility for the attacks, but suspicion is likely to fall on the Pakistani Taliban, known as Tehrik-e-Taliban Pakistan, or TTP.

Khan said Khawarij — a term used by the government for the outlawed Pakistani Taliban — has in recent months used drones to target security posts, raising concerns about the growing sophistication of such attacks.

Pakistan’s military killed at least 70 militants on Sunday in strikes along the Afghan border, targeting what authorities described as hideouts of Pakistani militants they blamed for recent attacks inside the country.

The TTP is separate from, but closely allied with, Afghanistan’s Taliban. Islamabad has accused the group of operating from inside Afghanistan, a charge both the TTP and Kabul deny.