Suspected Kurdish militants fired a rocket at an armored police vehicle and opened fire on a police station in the southeastern Turkish town of Cizre on Thursday, injuring two officers in a surge of violence threatening a fragile peace process.Security sources said the two officers were injured when their vehicle was hit by a rocket as they drove across a bridge while on patrol in the town. There was a brief gun battle as officers returned fire in the attack on the police station.Four people, two of them teenagers, have been killed over the past few weeks in clashes in Cizre.Some of the violence has been Kurdish infighting between Islamist Kurds and youth groups linked to the terrorist group Kurdistan Workers Party (PKK) militants, but Kurdish protesters have also clashed with the Turkish police.The violence highlights the fragility of a two-year-old peace process between Turkey and the terrorist group PKK, a militant group that has waged a three-decade insurgency for greater Kurdish autonomy, in which more than 40,000 people have been killed.Thirty-five people died in early October last year after Kurds rioted in several southeastern cities over what they perceived to be the government's refusal to help Syrian Kurds fighting the self-proclaimed Islamic State militants in the besieged Syrian border town of Kobani.The PKK is designated a terrorist group by Ankara, the United States and European Union.