Four children were killed on Friday when a mortar shell hit a civilian vehicle in which a family was attempting to flee violence in the troubled northwestern region of Pakistan, local media reported. A woman was injured.

The family was among some 1,500 families who have been ordered by Pakistani security forces to evacuate parts of Bara tehsil in Khyber Agency, where a majority of violence takes place. The evacuations were ordered in preparation of a military operation to combat militants in the region.

Officials told the Express Tribune newspaper that four children were killed while a woman was injured, although her condition was not immediately known. The report did not indicate whether the mortar shell was fired by Pakistani security forces or by militants in the area, and a military spokesperson did not immediately respond to a request for comment.

Those evacuating Bara tehsil have been told to move to either Peshawar or Jalozai camp, the largest camp for internally displaced persons in the country. The United Nations Refugee Agency previously stated that around 230,000 people are currently registered at the camp, where they are being provided with basic humanitarian supplies.

In 2009, more than two million people were displaced by violent clashes between Government troops and militants in northwestern Pakistan. The clashes led to one of the largest displacement crises in the world.