The editor of one of Turkey's leading newspapers, who was recently released after three months in detention, vowed Wednesday to expose the government's "crimes" when his trial begins later this month.

The Cumhuriyet newspaper's editor-in-chief Can Dundar and Ankara bureau chief Erdem Gul were released from jail last week by Turkey's top court but still face charges of revealing state secrets and espionage.

EU president Donald Tusk said Tuesday he would press Ankara for "a more intensive engagement" in the migrant crisis when he meets Turkey's president and prime minister later this week.

An independent pro-Kurdish television channel in Turkey said Saturday the authorities had ordered it to be taken off air on accusations that it broadcast "terrorist propaganda" for militants.

IMC TV said in a statement that Ankara prosecutors had sent a letter to Turkey's leading satellite operator Turksat ordering it to drop the channel and the request was immediately fulfilled.

Turkey believes the Kurdistan Workers Party (PKK) is no longer listening to its jailed leader Abdullah Ocalan and there is now no point in allowing him to make public statements, a senior Turkish official said on Friday.

Turkish presidential spokesman Ibrahim Kalin told foreign reporters that Ocalan, jailed on the Turkish prison island of Imrali, had effectively lost control over its military leadership based on Qandil mountain in northern Iraq.

Turkey is prepared to take further measures against Kurdish fighters in Syria beyond its current artillery bombardment and does not rule out air strikes on their positions, a senior official said on Friday.

Presidential spokesman Ibrahim Kalin told foreign reporters at a briefing that Ankara was dismayed at the level of support given by the United States to the People's Protection Units (YPG) militia, which Turkey considers to be a terror group linked to its own Kurdish militants.

Saudi jets on Friday arrived at a Turkish base to join the air campaign against Islamic State jihadists in Syria only hours before a ceasefire is to take force, local media reported.

Four F-15 jets landed at Incirlik air base in the Adana province in southern Turkey, the state-run Anatolia news agency reported.

EU migration commissioner Dimitris Avramopoulos on Friday warned that failure to make progress with Turkey at a March summit on stemming the migrant tide would spell "disaster" for the bloc.

"If there is no convergence and agreement on March 7, we will be led to disaster," Avramopoulos told a conference in Delphi, central Greece.

Turkey on Friday expressed alarm over the viability of an upcoming ceasefire agreed between Syria's warring parties, as the Syrian regime and its ally Russia pressed ahead with an offensive.

"We support the ceasefire in principle. Turkey has played an active role in the making of this decision," presidential spokesman Ibrahim Kalin told reporters in Ankara.

Two Turkish journalists held in jail for the last three months on hugely controversial charges of revealing state secrets were released early Friday after Turkey's Constitutional Court ruled their rights had been violated.

The Cumhuriyet newspaper's editor-in-chief Can Dundar and Ankara bureau chief Erdem Gul emerged from the Silivri jail on the outskirts of Istanbul before dawn to be greeted by jubilant supporters and family, television pictures showed.

Turkey's constitutional court on Thursday ruled that the rights of two Turkish opposition journalists charged with revealing state secrets in a hugely controversial case had been violated, paving the way for their release after three months in jail.

The Cumhuriyet newspaper's editor-in-chief Can Dundar and Ankara bureau chief Erdem Gul have been detained since November over a report alleging that President Recep Tayyip Erdogan's government tried to ship arms to Islamists in Syria.