At least four female development workers were killed after unidentified attackers shot their vehicle in troubled North Waziristan, police officials said.

Islamabad, Pakistan – According to the police, at least four female development workers were killed in a targeted attack in northwest Pakistan’s North Waziristan district. This was the latest attack on escalating violence in an area that was once the headquarters of the Pakistani Taliban.

The attack took place on Monday at 9:30 am (04:30 GMT) near the village of Ippi, a few kilometers east of the town of Mir Ali, senior police officer Shafiullah Gandapur Al Jazeera said by phone.

The workers’ vehicle was shot at by unidentified attackers who then fled the scene, he said. The driver of the vehicle was wounded and is being treated at a local hospital.

“This is a militant district, the threat is everywhere,” said Gandapur when asked if there is a specific threat to aid workers in the area.

“And in the tribal culture where women roam free, this is seen as unacceptable.”

The violence decreased

North Waziristan was once the headquarters of the Tehreek-e-Taliban Pakistan (TTP, also known as the Pakistani Taliban), an umbrella organization of armed groups that was founded in 2007 to try to overthrow the Pakistani government and establish a form of government consistent with it their strict interpretation of religion.

The TTP has severely restricted the free movement of women in areas under their influence and banned most development activities by non-governmental organizations.

After a series of military operations, the Pakistani military launched a new push against the TTP in North Waziristan in 2014. He succeeded in relocating the leadership of the group to eastern Afghanistan and worsening its operational capacities on Pakistani soil.

Since then the violence has decreased significantly, although sporadic attacks by the TTP continue to hit civilians and security forces alike.

Since last year, targeted attacks in North Waziristan have risen sharply as internally displaced people have returned to their homes after years.

More than 58 people were killed in the attacks last year, including tribal leaders, security forces and others. This emerges from a balance sheet derived from local media reports.

On Friday, according to a military statement, a soldier and two people identified as “terrorists” were killed in an exchange of fire in the North Waziristan district.

Police officer Gandapur said police in the area launched a search and strike operation and cordoned off the area following the attack on Monday.

Asad Hashim is Al Jazeera’s digital correspondent in Pakistan. He tweeted @AsadHashim