U.S. was 'warned' Turkish troops would attack Kurdish enclave in northern Syria

Turkey advised the United States ahead of its airstrikes in Syria against U.S.-backed Kurdish militia, and Washington is in contact with Ankara about the way forward, U.S. Defense Secretary Jim Mattis said Sunday.

"Turkey was candid," Mattis said. "They warned us before they launched the aircraft they were going to do it, in consultation with us. And we are working now on the way ahead. We'll work this out."

Turkish troops and Turkey-backed Syrian opposition forcesattacked theKurdish enclave in northern Syria on Sunday in their bid to drive a U.S.-allied Kurdish militia from the region.

Turkish officials said the troops entered the enclave of Afrin a day after dozens of Turkish jets and Turkish artillery units at the border pounded Syrian Kurdish targets as part of an offensive, code-named Olive Branch, that came on the heels of sharp threats from Turkey's leaders.

Turkey considers the Syrian Kurdish militia, known as the People's Protection Units, or YPG, a terror organization and a security threat because of its affiliation to Kurdish rebels fighting in southeastern Turkey.

The group controls Afrin, in Syria's northwestern corner, as well as a swath of territory along Turkey's border. The YPG also forms the backbone of the Syrian Democratic Forces, the main U.S. ally against ISIS in Syria.

SDF spokesperson Mustafa Bali denied that Turkish troops had entered Afrin, saying Kurdish forces had been repelling attacks since Saturday.

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The Britain-based Syrian Observatory for Human Rights also counteredTurkish claims, saying that while Kurdish militia and Turkish forces have clashed on the northern and western edges of Afrin, Turkish troops have failed to advance.

Turkey has prepared around 10,000 Syrian fighters to stormAfrin, accordingRamiAbdurrahman, director of the group.

The KurdishHawarNews agency says at least sevencivilians werekilled in theairstrikeson the village ofJilbrainsoutheasternAfrin. The Syrian Observatory said theairstrikeskilled eight, including a child in the village.

The group said theairstrikesbring to 18 the total number of civilians killed so far since the launch of the Turkish military offensive onAfrinon Saturday.

Turkey to set up secure zone

Turkish President Recep Tayyip Erdogan has promised to expand the operation to other Kurdish regions. Turkish media reports have quoted Prime Minister Binali Yildirim as telling a group of journalists on Sunday that Turkey aims to create a 30-kilometre-deep "secure zone" in Afrin.

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Turkish Gov.MehmetTekinarslansaid that suspected Syrian Kurdish fighters fired rockets from across the border early Sunday, slightly wounding one person.

He saidfour rockets struck the town ofKilis, hitting two houses and an office. He saidTurkish artillery returned fire.

Syrian fighters to storm Afrin

A Syrian commander, speaking to the AP by phone from northern Syria, said there were thousands of Turkey-backed fighters positioned in Azaz, at the frontier with the Kurdish enclave, awaiting orders. Another commander said hundreds more were stationed in Atmeh, south of Afrin. The officials spoke on condition of anonymity because they were not authorized to speak to the media.

Turkish leaders were infuriated by an announcement by the U.S. military this week that it was going to create a 30,000-strong border force with the Kurdish fighters to secure northern Syria. Days later, Secretary of State Rex Tillerson announced that the U.S. would maintain a military presence with the Kurds for the foreseeable future.

Erdogan, speaking in the Turkish city of Bursa on Sunday,said he hopes Turkey will conclude this particular operation in Syria in a short period of time.