Istanbul. Kurdish militants who have waged a 40-year insurgency in Turkey declared a ceasefire on Saturday in what could mark a significant boost to President Recep Tayyip Erdogan's government, two days after their imprisoned leader called for the group to disarm.

The announcement by the Kurdistan Workers' Party, or PKK, comes against the backdrop of fundamental changes in the region, including the reconfiguration of power in neighboring Syria after the toppling of President Bashar Assad, the weakening of the Hezbollah militant movement in Lebanon, and the Israel-Hamas war in Gaza.

While the government is yet to respond in detail to the PKK's declaration, Erdogan warned that Turkey would “always keep our iron fist ready in case the hand we extend is left in the air or bitten.”

Speaking at a Ramadan fast-breaking dinner in Istanbul, Erdogan added: “We will continue our ongoing (military) operations, if necessary, until we eliminate the last terrorist without leaving a single stone on top of another, without leaving a single head on his shoulder.”

The conflict between Turkey and the PKK has led to tens of thousands of deaths since it began in 1984. The ceasefire is the first sign of a breakthrough since peace talks between the PKK and Ankara broke down in the summer of 2015.

The PKK declaration was published by the Firat News Agency, a media outlet close to the group, on Saturday. It referred to the insurgents' leader, Abdullah Ocalan, who has been imprisoned by Turkey since 1999.

“We declare a ceasefire effective today to pave the way for the implementation of Leader Apo’s call for peace and democratic society. None of our forces will take armed action unless attacked,” it said, referring to Ocalan by his nickname.

Campaign of Pressure on Kurds
On Thursday, a delegation of Kurdish politicians announced Ocalan’s call for the PKK to lay down its arms and disband after visiting him on his island prison.

In its statement, the PKK's executive committee said Ocalan’s call indicated that a “new historical process has begun in Kurdistan and the Middle East.” Kurdistan refers to the parts of Turkey, Iraq, Syria and Iran inhabited by Kurds.

While stating that it would “comply with and implement the requirements of the call from our own side,” the PKK emphasized that “democratic politics and legal grounds must also be suitable for success.”

Ocalan's call came as the main pro-Kurdish political party in Turkey has faced pressure, with several of its mayors being removed from office in recent months and replaced by government appointees.

The PKK also appealed for Ocalan to be released from Imrali prison, located in the Marmara Sea, to “personally direct and execute” a party congress that would lead to the militants laying down their arms.

‘Opportunity to Take A Historic Step’
The peace initiative between the Turkish state and the PKK, which is considered a terrorist organization by Turkey and its Western allies, was started in October by Erdogan’s coalition partner, Devlet Bahceli, a far-right politician who suggested that Ocalan could be granted parole if his group renounces violence and disbands.

Erdogan said Ocalan’s message was a “new phase” in peace efforts in Turkey.

“There is an opportunity to take a historic step toward tearing down the wall of terror that has stood between (Turkish and Kurdish peoples’) 1,000-year-old brotherhood,” Erdogan said on Friday.

Some believe the main aim of the reconciliation effort is for Erdogan’s government to garner Kurdish support for a new constitution that would allow him to remain in power beyond 2028, when his term ends.

Bahceli has openly called for a new constitution, saying it was essential for Turkey's future that Erdogan remain in power. Erdogan and Bahceli are reportedly seeking parliamentary support from the pro-Kurdish People’s Equality and Democracy Party, or DEM.

“There will be a series of meetings next week, including state officials and politicians, and many things will become clearer and more concrete. We hope that everything will be arranged in the next three months,” said Sirri Sureyya Onder, one of the DEM members who visited Ocalan in prison on Thursday.

Isolated Attacks Inside Turkey
Ocalan, 75, wields significant influence in the Kurdish movement despite his 25-year imprisonment, during which the PKK has been led by top figures who have fled and found sanctuary in the Kurdish region in northern Iraq.

In Syria, Kurdish fighters -- who have ties to the PKK -- have been involved in intense fighting with Turkish-backed forces on the ground there.

The leader of the US-backed, Kurdish-led Syrian Democratic Forces has said Ocalan’s call for a ceasefire does not apply to his group in Syria.

The Turkish government, however, says all Kurdish groups it claims are tied to the PKK -- whether in Turkey, Syria, or Iraq -- must disband.

In recent years, the PKK has been limited to isolated attacks inside Turkey as the Turkish military, backed by armed drones, has pushed PKK insurgents increasingly across the mountainous border into Iraq.