Factbox-The Kurdish PKK militants who could renew peace talks with Turkey

The Kurdistan Workers Party (PKK) militant group could potentially restart peace talks with the Turkish government, after President Tayyip Erdogan's main ally last week revived hopes of ending the 40-year-old conflict.

But underscoring the difficult road ahead, just one day after Erdogan's ally Devlet Bahceli made his proposal, the PKK claimed responsibility for a deadly attack on a defence industry firm in Ankara, prompting Turkey to hit back at the militia in Iraq and Syria.

Here are details about the group:

WHAT IS THE PKK?

* The PKK is a militant group founded by Abdullah Ocalan in southeast Turkey in 1978 with an ideology based on Marxist-Leninist ideas.

WHAT DOES THE GROUP WANT?

* The PKK launched its insurgency against Turkey in 1984 with the initial aim of creating an independent Kurdish state. It subsequently moderated its goals to seeking greater Kurdish rights and limited autonomy in southeast Turkey.

* More than 40,000 people have been killed in the conflict, most of them militants. Much of the fighting in the past was focused in rural areas of mainly Kurdish southeast Turkey, but it has also conducted attacks in urban areas.

* The PKK is listed as a terrorist organisation by Ankara, the United States and the European Union.

WHAT IS THE GROUP'S HISTORY?

* The PKK operated in Syria until 1998 when Ocalan had to flee amid growing Turkish pressure. He was captured by Turkish special forces several months later in Kenya and sentenced to death by a Turkish court in 1999. The sentence was commuted to life imprisonment in October 2002 after Turkey abolished the death penalty and he is still imprisoned on an island near Istanbul. Fighting dwindled after Ocalan's capture, which also led to many PKK unilateral ceasefires and to the withdrawal of rebel fighters from Turkey.

* After a later flare-up in violence, Turkey and the PKK became involved in peace talks from late 2012. But that process and ceasefire collapsed in July 2015, unleashing the bloodiest period of the conflict and resulting in extensive destruction in some urban areas of southeast Turkey.

* Last week Erdogan's ally Bahceli, leader of Turkey's Nationalist Movement (MHP), said in a surprise suggestion that Ocalan could be allowed to speak in the Turkish parliament, if he announces an end to the group's insurgency, in exchange for the possibility of being released.

* Following Wednesday's attack at the headquarters of the Turkish Aerospace Industries (TUSAS) in Ankara, Bahceli returned to his usual stance on Monday, calling for the "root of treason" to be dried up, and adding that Ankara was determined to "remove terror from our lives".

WHERE IS THE CONFLICT FOCUSED NOW?

* In recent years the conflict has moved from southeast Turkey to be focused mainly in northern Iraq, where the PKK has mountain bases. Turkey has dozens of outposts in Iraqi territory and has launched operations against the militants there. It often carries out air strikes with warplanes and combat drones.

* Iraq has repeatedly said the air strikes and operations violate its sovereignty, but the two neighbours have in recent months agreed to ramp up cooperation against militants in the region. Iraq has labelled the PKK a "banned organisation" for the first time.

* Turkey also targets the YPG militia in Syria, regarding it as a PKK affiliate, and has conducted cross-border operations to push the group back from its border. However the YPG is also the spearhead of the primary ally of the U.S.-led coalition against Islamic State. Washington's support for the SDF has been a source of U.S.-Turkey tension for years.

* Turkey has also been working to normalise ties with Syrian President Bashar al-Assad's government after more than a decade of hostility, during which Ankara backed rebels looking to oust him. It has extended an invitation to Assad to hold talks on a possible rapprochement, but little progress has been made so far.