PESHAWAR, (Reuters) – A bomb exploded on a bus on the outskirts of the northwestern Pakistani city of Peshawar on Friday, killing 19 people and wounding several, police officials said.

There have been numerous bombings in Peshawar, capital of the Khyber-Pakhtunkhwa province, since the Pakistani military stepped up operations against militant groups in 2007.

“The bus was carrying around 40 people, most of them government employees, when there was a huge blast,” police official Merah Khan told Reuters.

Police said the bus was travelling from Peshawar to the nearby town of Charsadda.

Peshawar borders Pakistan’s semi-autonomous ethnic Pashtun regions along the Afghanistan border where Islamist militants have found refuge despite a series of military offensives over the past few years.

The Pakistani Taliban, the Afghan Taliban, al Qaeda and affiliated militant groups are entrenched in the tribal regions, and take advantage of the porous border to launch attacks against NATO and Afghan forces in Afghanistan.