DIYARBAKIR, Turkey (Reuters) - Six police officers were killed and four others wounded when a car bomb exploded as a police vehicle passed in southeastern Turkey on Monday in an attack that security sources said appeared to have been carried out by Kurdish militants.

The bomb was detonated by remote control as the vehicle passed through a road in Bingol province. The attack was carried out by the members of the outlawed Kurdistan Workers Party (PKK), the sources said.

Two of those injured were in serious condition.

The PKK, listed as a terrorist organization by Turkey, the United States and European Union, has waged an armed campaign against security forces in the mainly Kurdish southeast since 1984, pushing for Kurdish autonomy. More than 40,000 people, mostly Kurds, have died in the violence.

Unrest has flared anew since a ceasefire collapsed in July 2015, and thousands of militants and hundreds of soldiers and police have since died. Rights groups have said about 400 civilians have also perished.

Turkey’s military, NATO’s second largest, is undergoing a major shake-up following a July 15-16 coup attempt, but has played down concerns that the wide-reaching changes will undermine its struggle against the PKK.