Turkey on Saturday launched operation "Olive Branch" seeking to oust from the Afrin region of northern Syria the YPG which Ankara considers a terror group.

Prime Minister Binali Yildirim said troops crossed into the YPG-controlled region in Syria at 0805 GMT, the Dogan news agency reported.

Turkish artillery and war planes pounded YPG sites around Afrin and total of 153 targets, including YPG refuges and weapons stores have now been hit, according to the army.

The state-run Anadolu news agency said the Turkish troops, whose number was not specified, were advancing alongside forces from the pro-Ankara rebel Free Syrian Army (FSA) and were already five kilometres (three miles) inside Syria.

The operation is Turkey's second major incursion into Syria during the seven-year civil war after the August 2016-March 2017 Euphrates Shield campaign in an area to the east of Afrin against both the YPG and IS.

The YPG said that after the first strikes on Saturday 10 people were killed, including seven civilians. The Turkish army said there were casualties but insisted they were all members either of the YPG or the PKK, AFP reported.

A YPG spokesman claimed that the Turkish forces had sought to enter Afrin "but we blocked the attack".

There was no immediate comment from the United States on the offensive but ahead of its launch a senior State Department official had raised concerns it risked being harmful for security in the region.

The Russian foreign ministry voiced concern and urged Turkey to show restraint. And the defense ministry said its troops were withdrawing from the Afrin area to ensure their security and prevent any "provocation".

Timur Akhmetov, Ankara-based researcher at the Russian International Affairs Council, told AFP that Russia appeared to have given the "green light" to the operation but made clear it should not lead to destabilization elsewhere.

"I don't think Russia will agree to let Turkey occupy the whole Afrin region and insists on keeping the Syrian government in charge," he added.

Reporter’s code: 50101