FACTBOX: Turkish incursions into northern Iraq

(Reuters) - Turkey's military said on Friday it had launched a cross-border land offensive into northern Iraq on Thursday, backed by fighter aircraft, to hunt down Kurdish PKK guerrillas who have moved from Turkey to bases in Iraq.

Here are some details of previous Turkish incursions into Iraq against Kurdish rebels:

* BACKGROUND:

-- The Kurdistan Workers Party (PKK or Kongra-Gel), founded in 1978 as a Marxist-Leninist insurgent group.

-- The PKK is considered a terrorist organization by the United States and the European Union. It has been blamed for the deaths of nearly 40,000 people since it launched its armed struggle for an ethnic homeland in southeast Turkey in 1984.

-- Washington and Baghdad have taken no action against the estimated 3,000 PKK guerrillas hiding in northern Iraq, despite repeated Turkish appeals.

* PRESSURE MOUNTS:

-- Turkey's government has come under public pressure to act because PKK attacks from bases in northern Iraq have killed scores of Turkish troops.

-- It has sent 100,000 troops to the border and carried out a series of small bombing and ground raids, despite U.S. worries that this could destabilize northern Iraq.