Top Iraqi Shiite cleric Grand Ayatollah Ali al-Sistani on Saturday demanded the release of 18 Turkish workers kidnapped in Baghdad by unknown militants, saying it harmed the image of Islam.

The Turkish men, who were working on a football stadium project, were seized in Baghdad's Sadr City area earlier this month, and militants presenting themselves as a Shiite group claimed the kidnappings in a video posted online.

A Turkish court on Friday handed a suspended prison sentence of 11 months and 20 days to a 17-year-old schoolboy convicted of insulting President Recep Tayyip Erdogan, in a case that raised new concerns about freedom of speech in the country.

The boy, identified as M.E.A., was convicted of "insulting the president" while speaking at a public meeting in the central city of Konya in December 2014.

An unknown militant group has claimed the kidnapping of 18 Turkish workers in Iraq and issued a list of demands it said Ankara must fulfill for them to be released.

Gunmen seized 18 employees of major Turkish construction firm Nurol Insaat on September 2 in the Sadr City area of northern Baghdad, where they were working on a football stadium project.

Turkish warplanes struck 64 Kurdistan Workers Party (PKK) targets in overnight raids on northern Iraq, dropping 80 bombs, the Turkish media reported Friday.

At least 60 PKK militants were killed in the strikes, carried out by 21 Turkish F-16 and F-4 warplanes, the state-run Anatolia news agency reported, quoting security sources.

Turkey on Friday said it would lift a week-long curfew in a southeastern city imposed to support a military operation against Kurdish rebels but which has also fueled fears of a possible humanitarian crisis.

The curfew in Cizre, in place since September 4, will end on Saturday at 7:00 am (0400 GMT), said the statement from Sirnak region governor Ali Ihsan Su.

One civilian was killed and three Turkish police wounded on Friday when suspected Kurdish militants opened fire on a cafe in the southeastern city of Diyarbakir, security sources said.

A small group of police were in a cafe in the centre of Diyarbakir specialising in tripe soup, a popular breakfast staple, when suspected Kurdistan Workers' Party (PKK) militants opened fire.

Iraq on Thursday condemned Turkey for sending ground troops onto its territory in pursuit of Kurdish rebels, calling it a "clear violation" of its sovereignty.

"The foreign ministry expresses its condemnation of the incursion of a number of Turkish military units inside Iraqi territory," spokesman Ahmed Jamal said in a statement.

A Turkish soldier deployed on the border with Syria was killed early on Thursday by fire from Syrian territory, the Dogan news agency reported.

The soldier, 21, was standing guard in the Reyhanli district of the Hatay region of southern Turkey when he was hit by fire from the Syrian side of the border.

Deputies from Turkey's pro-Kurdish People's Democratic Party (HDP) on Wednesday began marching on a Kurdish city in the southeast that has been under curfew for six days amid growing alarm over a humanitarian crisis.

HDP co-leader Selahattin Demirtas and Ali Haydar Konca and Muslum Dogan, who represent the party in the Turkish caretaker cabinet, had sought to get to the town of Cizre in the southeastern Sirnak province by vehicle.

A Dutch journalist based in Kurdish-majority southeast Turkey is to be deported after being detained last week during clashes between Kurdish rebels and the Turkish security forces, her lawyer said on Wednesday.

Frederike Geerdink was detained last weekend while traveling with a delegation from the pro-Kurdish Peoples' Democratic Party (HDP) in the Yuksekova district of Turkey's southeastern Hakkari region.