People in Akcakale Sanliurfa province, southeastern Turkey, at the border with Syria, watch smoke billowing inside Syria, during bombardment by Turkish forces on Thursday, October 10. AP Photo/Emrah Gurel.

UNITED NATIONS - The United States warned Turkey at the United Nations on Thursday that it faced "consequences" if its assault against Kurdish militias in northeast Syria did not protect vulnerable populations or contain Islamic State militants.

US Ambassador to the United Nations Kelly Craft, speaking after a closed-door meeting of the UN Security Council on Syria, did not specify what those consequences could be.

Turkey pounded US-allied Kurdish militia in Syria for a second day on Thursday, forcing tens of thousands of people to flee and killing dozens.

"Failure to play by the rules, to protect vulnerable populations, failure to guarantee that ISIS cannot exploit these actions to reconstitute, will have consequences," Craft told reporters.

The 15-member Security Council met at the request of the five European nations: Britain, France, Germany, Belgium and Poland. In a joint statement, the European states called on Turkey to stop its military action.

"Renewed armed hostilities in the northeast will further undermine the stability of the whole region, exacerbate civilian suffering and provoke further displacements," they said in a statement read to reporters by Germany's Deputy U.N. Ambassador Jurgen Schulz.

The offensive was launched days after US President Donald Trump pulled US troops out of the way in an abrupt policy shift that followed a phone conversation with Turkish President Tayyip Erdogan on Sunday.

Turkey says the Kurdish YPG, the main component of the US-backed Syrian Democratic Forces, is a terrorist group linked to Kurdish insurgents that have fought in Turkey for years.

Trump denied he had abandoned the Kurdish forces, the most effective US partners in fighting Islamic State (ISIS) in Syria.

Turkey told the UN Security Council in a letter on Wednesday that its military operation in northern Syria would be "proportionate, measured and responsible."

"The operation will only target terrorists and their hideouts, shelters, emplacements, weapons vehicles and equipment," Turkey's UN Ambassador Feridun Sinirlioglu wrote. "All precautions are taken to avoid collateral damage to the civilian population."

Turkey justified its action under Article 51 of the UN Charter, which covers an individual or collective right to self-defense against armed attack.

The UN Security Council is discussing a US-drafted statement, but it appeared unlikely they could reach an agreement. Such statements are agreed by consensus.

"It should take into account other aspects of the Syrian crisis not just the Turkish operation. It should speak about the illegal military presence in that country," Russian UN Ambassador Vassily Nebenzia told reporters, referring to the presence of US troops in Syria. 

Reuters