FACTBOX: Who are the PKK?

(Reuters) - Fifteen Turkish soldiers have been killed in clashes with Kurdish separatist PKK rebels in southeast Turkey. Following are some facts about the PKK:

* BEGINNINGS:

-- Abdullah Ocalan founded the party in 1974 and it adopted the name Kurdistan Workers Party (PKK) in 1978, a Marxist-Leninist insurgent group fighting for an independent Kurdish state.

* FIGHT FOR A HOMELAND:

-- The PKK took up arms against Turkey in 1984 with the aim of creating an ethnic homeland in the southeast. Nearly 40,000 people have been killed in the conflict since then.

-- Ocalan was captured and sentenced to death by a Turkish court in 1999 but the sentence was reduced to life imprisonment in October 2002 after Turkey abolished the death penalty.

-- Fighting dwindled after Ocalan's capture and it also led to a ceasefire and the withdrawal of rebel fighters from Turkey.

* A POLITICAL STRUGGLE:

-- Ocalan, after his capture, emphasized the importance of winning rights for the Kurds through political rather than armed struggle. That encouraged the rebels to establish a new political wing known as KONGRA-GEL in November 2003.

* VIOLENCE FLARES AGAIN:

-- In June 2004, the PKK announced the end of its ceasefire and told investors and tourists to stay away from Turkey.

-- In April 2006 authorities blamed the PKK for rioting between pro-Kurdish protesters and security forces in Turkey's southeast in the worst civil unrest since the mid-1990s.

* FIGHTING RESUMES:

-- Some 3,000 PKK fighters are based in northern Iraq and have attacked security and civilian targets in Turkish territory. A few thousand PKK rebels also are believed to be in Turkey.

-- The border region saw fierce fighting in late 2007 and in response to growing internal pressure thousands of Turkish troops crossed into northern Iraq in February 2008 in their hunt for PKK guerrillas. Eight days later Turkish armed forces withdrew. The army said that it killed 242 rebels out of 300 targeted in the operation and PKK communications were cut.

-- There have been sporadic violent incidents in the region in recent months.

-- On Friday, 15 Turkish soldiers were killed in clashes in southeast Turkey. At least 23 members of the PKK were also killed after rebels armed with "heavy weapons" attacked a military outpost in the Semdinli region bordering Iraq and Iran, the military said.