DIYARBAKIR, Turkey (Reuters) - A Turkish police officer was killed and two wounded when suspected Kurdistan Workers Party (PKK) militants fired a rocket at their armored vehicle in the town of Nusaybin near the southeastern border with Syria, security sources said on Sunday.

Turkey's predominantly Kurdish southeast has been engulfed in its worst violence since the 1990s after a two-year ceasefire between the state and PKK, which has waged a three-decade insurgency for Kurdish autonomy, collapsed last July.

The conflict has complicated international efforts to end the war in neighboring Syria.

Ankara says the Syrian Kurdish YPG militia, which has won U.S. support in the fight against Islamic State, has deep ties to the PKK and fears that its territorial gains in northern Syria will stoke Kurdish separatism inside Turkey.

The PKK, considered a terrorist group by Turkey, the United States and the European Union, launched a separatist armed rebellion against the Turkish state in 1984 in a conflict that has killed more than 40,000 people, mostly Kurds.

PKK fighters have sealed off entire districts of some towns and cities in the southeast and declared autonomy, prompting the security forces to step up their operations.

(Reporting by Seyhmus Cakan; Writing by Nick Tattersall; Editing by Janet Lawrence)