Turkish warplanes have launched air strikes against Kurdish positions in northern Syria, in a move that may cause tensions with the US. UU
Turkey is seeking to expel the Kurdish fighters from Afrin, held by them since 2012. Some of these forces helped the US. UU to fight against the Islamic State group.
There are also reports of pro-Turkish Syrian rebels advancing in the city.
Turkey says it is launching a full military operation against these Kurds, which it considers a terrorist group.
President Recep Tayyip Erdogan also threatened to attack the city of Manbij, about 100 kilometers from Afrin in another Kurdish area, as the next target.
Russia, a key military figure in the region, says it is concerned about the reports, but said earlier it would not interfere with the conflict.
Syria previously warned against any operation and said it would shoot down Turkish planes.
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Why is P Erdogan resident threatening groups supported by the United States?
The Kurdish YPG (units of protection of the Kurdish Syrian people) has been a key part of the battle against the group calling itself the Islamic State in Syria, and has been backed by the United States.  Turkey, however, believes that the group has links to the outlawed Kurdistan Workers' Party (PKK) and has threatened to eliminate Kurdish fighters from both Afrin and Manbij for several months.
It seems that his plans have accelerated announcement of the USA. UU that it will help the Syrian Democratic Forces (SDF) – an alliance against IS of which the YPG is a member – will build a new "border security force" to prevent the return of IS.
The YPG and SDF deny any terrorist link, a claim backed by the US government. UU
But President Erdogan called the border force "terrorist army."
Speaking at a meeting of his AKP ruling party, Erdogan once again linked the YPG and other Syrian Kurdish groups to the Turkish PKK, an insurgent group considered a terrorist organization by Turkey.
"The PKK, YPG, PYD are all the same, changing the names does not change the fact that they are terrorist organizations," the Turkish news agency Anadolu quoted him as saying.
Disagreement over Kurdish fighters has created a sharp division among NATO allies.
The US State Department UU He has appealed to calm and tried to downplay the representations of a new "border force", describing the new development as security training.
"We do not believe that a military operation … will serve the cause of stability, Syrian stability, or indeed Turkish concerns about the security of its border," he said.
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What happened in Afrin?
On Saturday, the Turkish military announced that a new campaign, dubbed "Olive Branch", had begun at 14:00 GMT, targeting the YPG and IS jihadists.
The operation would be carried out "with respect to the territorial integrity of Syria," he added.
Turkish state media also reported that Syrian fighters backed by Turkey had begun to move towards the Afrin region.
The Turkish army has bombed the area since Thursday, an action it said was in response to fire from the area.
On Saturday, the SDF accused Turkey of using the bombing as a smoke screen before launching an offensive. A spokesman for the group told the Reuters news agency that he would have no choice but to defend himself if attacked.
Rizan Habou of the Syrian Democratic Council in Afrin told BBC Arabic that the residents were seeking refuge.
"When the villages in Afrin are bombed, civilians [including] women and children are forced to leave their homes and head to the open spaces and agricultural land relatively safer until the bombing is over"  "The YPG and the civilians will defend Afrin until the last moment".
Afrin is isolated from two other self-proclaimed Kurdish autonomous cantons – Kobani and Jazira.
Rebel forces backed by Turkey took a 100 km (60 mile) zone that separates the territories after expelling IS in 2016, so expelling Kurdish fighters would significantly expand Turkey's control area in the region .
What about Russia? ?
The Russian Ministry of Foreign Affairs says it is concerned about the news of the offensive, and is urging moderation. However, officials said earlier that Russia would not get involved in the conflict.
Russian Senator Frants Klintsevich, vice president of the defense and security committee, told the Interfax news agency that Moscow will only respond if Russian bases in Syria are threatened. .
He said that Russia has been in a difficult situation, since it has "good relations with both Damascus and Ankara."
Turkey's military and intelligence chiefs had tried to obtain Russia's agreement to allow Turkish aircraft to use the Russian-controlled airspace above Afrin.
Such consent is considered essential for any Turkish operation. Moscow is a key ally of Syrian President Bashar al-Assad and has a contingent of soldiers at the airport in the center of Afrin.
It is not yet clear whether Russia's claim that it will not interfere prevents the use of its airspace.
On Friday, the Turkish news agency Anadolu reported that Russian military personnel in Afrin were leaving in groups, but Russian Foreign Minister Sergei Lavrov later denied the reports.