Turkish President Recep Tayyip Erdogan on Monday predicted that Ankara's ally Azerbaijan would "one day" regain control of Nagorny Karabakh, as deadly clashes between Azerbaijani and Armenian forces over the region raged for a third day.

Turkish President Recep Tayyip Erdogan on Friday called on European countries to stop supporting the outlawed Kurdistan Workers' Party (PKK), days after a bombing claimed by Kurdish rebels killed 35 people in Ankara.

Erdogan warned Europe its cities faced the kind of repeated attacks that Turkey has suffered in recent months, some of which have been claimed by Kurdish fighters and others blamed on the Islamic State group.

Turkish President Recep Tayyip Erdogan said Wednesday he was ready to help combat terrorism in Nigeria, where Boko Haram fighters have killed thousands of people in a bloody campaign for a hardline Islamic state.

He also signed a memorandum on trade and economic cooperation, which Nigerian President Muhammadu Buhari said was "just the beginning of what we have in the pipeline."

Almost 2,000 people in Turkey have been prosecuted for insulting President Recep Tayyip Erdogan since he came to office in August 2014, a government minister said on Wednesday.

"The number of dossiers which have thus far allowed prosecution with regard to insulting the president is 1,845," Justice Minister Bekir Bozdag said during parliamentary questions, media reports said.

Turkish President Recep Tayyip Erdogan on Wednesday said Syrian Kurdish militia forces must remain outside the scope of a ceasefire agreed between Syria's warring parties, in a blow to the deal days before it is due to be enforced.

Lashing out at Western policy in Syria, he said the Syrian Kurdish Democratic Union Party (PYD) and its People's Protection Units (YPG) militia were a "terror group" just like Islamic State (IS) jihadists and the Al-Qaida affiliated Al-Nusra Front.

President Recep Tayyip Erdogan said on Friday that Turkey had "no doubt" that Syrian Kurdish fighters were behind an attack on a convoy of military buses in Ankara that left 28 people dead.

Turkey said on Sunday it would not abandon thousands of Syrians stranded on its border after fleeing a major Russian-backed regime offensive, as aid agencies warned of a "desperate" situation.

Tens of thousands of people, including many women and children, have been uprooted as pro-government forces backed by intense Russian anti-rebel air strikes advance near Syria's second city Aleppo.

Turkey said on Thursday it had summoned Iran's ambassador to protest attacks on Turkish President Recep Tayyip Erdogan in the Iranian press in the wake of a diplomatic crisis between Tehran and Riyadh.

Erdogan has refused to condemn Saudi Arabia's execution of prominent Shiite cleric and activist Sheikh Nimr al-Nimr this month. The execution sparked outrage in Shiite-majority areas of the Middle East, and protesters in Iran attacked two Saudi diplomatic missions, prompting Riyadh to sever diplomatic ties.

Turkish President Recep Tayyip Erdogan on Wednesday refused to condemn Saudi Arabia for its execution of 47 convicts including a prominent Shiite cleric, saying it was an "internal legal matter" of the kingdom.

"The executions in Saudi Arabia are an internal legal matter. Whether you approve or not of the decision is a separate issue," Erdogan said in a televised speech, his first reaction to the controversy which has raised tensions between Saudi Arabia and its regional rival Iran.

A U.S.-based Turkish preacher who has emerged as an arch-enemy of President Recep Tayyip Erdogan went on trial in absentia Wednesday along with several former police chiefs charged over the corruption allegations that hit the Turkish leader in 2013.

Fethullah Gulen, a former ally of Erdogan turned chief foe, was not present at the start of the proceedings in Istanbul, with Washington failing to grant Turkish requests for his extradition from his secluded compound in Pennsylvania.