ISTANBUL, Turkey (AFP) — Jailed PKK founder Abdullah Ocalan on Thursday called for his Kurdish militant group to lay down its weapons and dissolve itself in a landmark declaration read out in Istanbul.

“All groups must lay down their arms and PKK must dissolve itself,” he said in a declaration drawn up in his cell on Imrali prison island where he has been held in solitary confinement since 1999.

The call came four months after Ankara offered an olive branch to the 75-year-old who founded the Kurdistan Workers’ Party (PKK), which has led a decades-long insurgency against the Turkish state that has cost tens of thousands of lives.

“I am making a call for the laying down of arms, and I take on the historical responsibility of this call,” he said in a statement.

His words were read out by a delegation of lawmakers from the pro-Kurdish DEM party who visited him earlier on Thursday, the declaration sparking spontaneous applause inside the packed hall.

In the Kurdish-majority city of Diyarbakir in the southeast, where around 3,000 people had gathered at a square to listen to an audio broadcast of Ocalan’s call, some broke into spontaneous applause while others broke down in tears.

“Ocalan’s call for the PKK to disarm and disband represents a seismic shift. Not just for Turkey, which has waged a decades-long war against the group, but for the region at large,” said Hamish Kinnear, senior analyst at Verisk Maplecroft.

But his words elicited a cautious response from a senior figure within Turkish President Recep Tayyip Erdogan’s ruling AKP.

“If the terrorist organization heeds this call, lays down its arms and dissolves itself, Turkey will be freed from its shackles,” Efkan Ala, AKP’s deputy chairman, was quoted as saying by the state news agency Anadolu.

The big question is how his message will be received by fighters whose military leadership is mostly based in the mountains of northern Iraq.

French historian Boris James, who specializes in the Kurds, said the response could be nuanced.

“The PKK’s military leaders may accept it without it having any practical impact in the field,” he told AFP.

Of particular concern are those fighters allied with the US-backed Syrian Defense Forces (SDF) in northeastern Syria — a force under pressure from Damascus to disarm but which is fighting off attacks by Turkish-backed militia groups.

But Kinnear said much would depend on the response of the Turkey-based PKK elements.

“If the bulk of the Turkey-based PKK adheres to Ocalan’s call, PKK militants in Iraq and PKK-aligned groups in Syria are likely to follow suit,” he said.

Since Ocalan was jailed in 1999, there have been various attempts to end the bloodshed that erupted in 1984 and has cost more than 40,000 lives.

The last round of talks collapsed amid violence in 2015.

After that, there was no contact until October, when hardline nationalist MHP leader Devlet Bahceli offered Ocalan a surprise peace gesture if he would reject violence in a move endorsed by Erdogan.

Although Erdogan extended his full support for the rapprochement in late October, he has said little since.

And his government has cranked up pressure on the opposition, arresting hundreds of politicians, activists and journalists and removing 10 recently-elected DEM mayors, all of whom have been charged with “terror ties.”

Despite the wave of arrests, many are hoping Ocalan’s call will ultimately result in concessions for the Kurds, who make up around 20 percent of Turkey’s 85 million population.