The Latest on developments related to Syria (all times local):

11 p.m.

Turkish news footage shows several military trucks carrying tanks and other armored vehicles crossing through a border gate into a Turkish-controlled region ahead of an anticipated ground offensive into a Syrian Kurdish enclave.

The Dogan news agency carried footage showing the trucks late on Saturday moving through the border gate of Oncupinar, known as Bab al Hawa in Arabic, into the Turkish-controlled Syrian town of Azaz.

The deployment occurred hours after dozens of Turkish jets bombed Syrian Kurdish militia targets in the enclave of Afrin. Turkey says the enclave is run by Kurdish militia it considers an extension of Kurdish rebels fighting inside Turkey and a threat to its security.

Turkish Prime Minister Binali Yildirim said a ground operation was expected to begin on Sunday, depending on developments on the ground.

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10:10 p.m.

Turkish Prime Minister Binali Yildirim said a Turkish ground offensive into the Kurdish-held Syrian enclave of Afrin is likely to start on Sunday, depending on developments.

Yildirim said Saturday that Turkish jets had destroyed "almost all" targets they had determined to belong to a Syrian Kurdish militia, which Turkey considers to be a "terrorist" threat to Turkey.

He said Turkish artillery were continuing to shell the region.

Yildirim said: "As of tomorrow, depending on developments, our grounds elements will carry out the necessary activities."

The Turkish military said as many as 72 planes involved in the Afrin operation — codenamed "Olive Branch" — returned to their bases safely on Saturday.

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10 p.m.

Syria's Foreign Ministry has condemned Turkey for launching a military operation against a Kurdish group inside Syria's borders.

Turkey announced Saturday it was going to defeat the Kurdish People's Protection Units, known as YPG, in their enclave in Afrin in northern Syria.

The foreign ministry called the Turkish operation, codenamed "Olive Branch," an "aggression" and said Afrin was an "inseparable part of Syria."

Earlier this week, Syria's government threatened to shoot down Turkish jets if they attacked Syrian territory.

Turkey's warplanes attacked Afrin Saturday.

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8 p.m.

Turkey's state-run news agency says Turkish jets have attacked a military airport in northwest Syria that is under the control of a Syrian Kurdish military group.

Anadolu Agency said the jets struck Mannagh air base on Saturday as Turkey launched a military offensive to oust Syrian Kurdish militia it considers to be a security threat from the enclave of Afrin that they control.

Separately, the agency quoted Turkey's military officials as saying warplanes had so far struck 108 out of a total of 113 Syrian Kurdish militia targets in the Afrin region.

Turkish media meanwhile quoted Foreign Minister Mevlut Cavusoglu as saying that Turkey had informed the Syrian government about the Turkish offensive in Afrin "by writing."

The heads of missions of the embassies of the United States, Russia and Iran were also called to Turkey's Foreign Ministry to be briefed on the Turkish offensive.

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7:30 p.m.

Russia's Defense Ministry says it is pulling back troops that had been deployed near the Syrian city of Afrin after bombing strikes by Turkish warplanes.

In a statement reported on Russian news agencies, the ministry said Saturday that "to prevent possible provocations, to exclude the threat to life and health of Russian servicemen, the operational group of the Center for Reconciliation of warring parties and military police in the Afrin area is relocated to the Tell-Adjar area."

Tell-Adjar is within a so-called "de-escalation zone" established in September.

There were no immediate reports of how many Russian servicemen were affected by the move.

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6:35 p.m.

Turkish officials say Turkish Foreign Minister Mevlut Cavusoglu has discussed Turkey's military offensive in Syria with U.S. Secretary of State Rex Tillerson.

Separately, Turkey's chief of military staff Hulusi Akar spoke with his U.S. and Russian counterparts, Turkish media reports said.

Ministry officials said Saturday Tillerson requested a telephone conversation with Cavusoglu. They did not provide further details.

Saturday's offensive follows Turkish anger at a U.S. announcement of plans to create a 30,000 Kurdish-led "border security force" along the border of Turkey. Tillerson later said the U.S. plans were "misrepresented," in an apparent bid to appease Turkey.

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6:20 p.m.

Turkey's military says its offensive against a Syrian Kurdish-held enclave in northwest Syria has been codenamed operation "Olive Branch."

A military statement says the operation launched Saturday aims to protect Turkey's borders, "neutralize" Syrian Kurdish fighters in the enclave of Afrin and to save the local population from their "pressure and oppression."

It said the operation was launched at 5 p.m. local time.

The military said the operation was being conducted as part of Turkey's international right for legitimate self-defense.

It stressed Turkey's respect for Syria's territorial integrity, saying the offensive would target "terrorists," their shelters and weapons and that utmost care was being taken to ensure civilians are not harmed.

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5:30 p.m.

Turkish Prime Minister Binali Yildirim says Turkish jets have begun an aerial offensive against the Syrian Kurdish-held enclave of Afrin in northwestern Syria.

"As of this moment our brave Armed Forces have started the aerial offensive to eliminate the PYD and PKK and Daesh elements in Afrin," said Yildirim at a speech in the city of Bilecik, referring to the Kurdish Democratic Union Party and the Kurdistan Worker's Party respectively, and using an Arabic acronym for the Islamic State group

Turkey's state-run news agency, meanwhile, said that a group of Turkish-backed Syrian opposition forces crossed into the area on Saturday as part of an offensive to oust a militia group Turkey considers to be terrorists.

Associated Press journalists at the Turkish border saw at least five jets heading toward Afrin. They also witnessed a convoy of buses, believed to be carrying Syrian opposition fighters, traveling along the border across from Afrin. The convoy included trucks mounted with machine guns.

Rojhat Roj, a spokesman for the Syrian Kurdish militia group, confirmed that a Turkish plane was striking Afrin city.

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5 p.m.

Syrian state TV says government forces have retaken a key air base in northwest Syria that was lost to rebels in 2015.

The state broadcaster says Syrian troops fought their way into the strategic Abu Zuhour air base on Saturday, in Idlib province.

The capture is a significant coup for the government and allied militias who have fought their way deep into what was considered a stronghold for rebels and al-Qaida insurgents since launching operations in December.

But the advance has displaced more than 200,000 civilians, according to the U.N., exacerbating an already dire humanitarian situation in the north of the country.

The Britain-based Syrian Observatory for Human Rights monitoring group says pro-government forces are now in control of most of the air base after fierce clashes since this morning.

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4:30 p.m.

Turkish President Recep Tayyip Erdogan reiterated that a Turkish offensive against the Syrian Kurdish-controlled enclave of Afrin was "de facto" underway and added that it would be followed by an operation against another Kurdish-held territory.

Speaking in Turkey's western city of Kutahya , Erdogan said Turkey's next target would be the Syrian town of Manbij, which lies west of the Euphrates river, and which a U.S.-backed Kurdish-led forced seized from the Islamic State group in 2016.

Erdogan said: "The operation against Afrin has de facto started on the field. It will be followed by Manbij."

Turkey has massed troops and tanks along the border but there has been no indication yet that they have crossed into Syria. Turkish artillery has been shelling the region and, on Saturday, Turkey's military said it retaliated against fire into Turkey from Afrin.

Erdogan again accused the United States of not keeping a promise to force the Kurdish militia to leave Manbij after its capture from IS.

Said the Turkish leader: "Since promises concerning Manbij have not been met, no one has the right to say a word."

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4:20 p.m.

A group of prominent academics and human rights activists are urging the leaders of Russia, Iran and the United States to prevent Turkey from carrying out an offensive against a Syrian-Kurdish controlled enclave in northwest Syria.

The group, including scholar and activist Noam Chomsky, called Turkey's threat to attack Afrin a "blatant act of aggression against a peaceful and democratically-governed region and population."

Their statement, made available to The Associated Press on Saturday, praised the Syrian Kurdish militia group, known as the YPG, for their effective fight against the Islamic State group in Syria.

It said: "The U.S and international community have a moral obligation to stand behind the Kurdish people now."

Turkey views the YPG as an extension of outlawed Kurdish rebels fighting inside Turkey and has vowed to attack territories it controls in northern Syria.

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2:05 p.m.

The Islamic State group has announced the death of Denis Cuspert, the German-born rapper who went by the name Deso Dogg before giving up the profession and joining the militant group in Syria.

The group says Cuspert was killed in an airstrike on Wednesday in Syria. It published a notice of his death on an affiliated website on Saturday.

Cuspert, who toured in the U.S. in 2006, lent his voice to record anthems for the militants to use in recruiting videos they circulated online.

The U.S. government designated him a "global terrorist." The Pentagon said in 2015 Cuspert was killed in an airstrike before walking back the story in 2016.

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12:25 p.m.

Syrian state TV says government forces have reached the perimeter of a rebel-held air base deep inside what was once opposition territory in northwest Syria.

The station said on Saturday the government is attacking Abu Dhuhour base in Idlib province.

Pro-government forces reached the base earlier this month but pulled back 10 days ago to fight off a counter-offensive by rebels and al-Qaida-linked insurgents.

The Britain-based Syrian Observatory for Human Rights monitoring group says pro-government forces have surrounded Abu Dhuhour base from three sides.

Rebels took over the base in 2015 but have not been able to use it as an airfield because they do not have an air force.

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10:05 a.m.

Turkey's military says it has retaliated against fire into Turkey from across the border in a Kurdish-controlled enclave in northwest Syria.

A brief military statement said Saturday the military responded to two days of "harassment" by attacking refuges and shelters in the enclave of Afrin allegedly belonging to a Syrian Kurdish militia group that Turkey considers to be a "terror" organization. The military did not provide details.

Turkey has vowed to launch a ground operation into Afrin to eradicate the threat from the group it says is an extension of Kurdish rebels fighting inside Turkey. It has been massing troops and tanks at its border.

Turkey's defense minister said Thursday the offensive into Afrin had "de facto" started, in reference to sporadic Turkish military shelling of the area.