Turkey launched a long-planned operation in north-east Syria on Wednesday in a move widely condemned by governments around the world, and that US President Donald Trump was quick to say he did not endorse.
Soon after Turkish President Recep Tayyip Erdogan announced the start of "Operation Peace Spring", explosions were heard in the Syrian border town of Ras Al Ain.
Turkey’s Defence Ministry says Turkish ground forces moved across the border to fight against Kurdish fighters in northeastern Syria, hours after Turkish jets and artillery pounded areas in Syria’s northern border.
Turkey aims to create a “safe zone” that would be cleared of Kurdish fighters, who Ankara considers to be terrorists and an extension of Kurdish rebels fighting inside Turkey, and eventually allow for the return of refugees.
A Syrian war monitor and an activist collective in Kurdish-held areas say at least seven civilians have been killed in Turkish strikes in northeastern Syria.
The Britain-based Syrian Observatory for Human Rights put the death toll at eight, including two Christian Assyrians in the city of Qamishli, a husband and wife and their child as well as another man in a village outside of the town of Tal Abyad, and a child in a village west of Qamishli. Also killed was a man in Ras Al Ayn, it said.
The Rojava Information Center, an activist collective in northeast Syria, counted seven killed.
The Observatory said at least seven fighters from the Kurdish-led Syrian Democratic Forces were killed in the fighting. The Rojava center put the death toll at three.
The Syrian Democratic Forces said the air strikes were aimed at civilians, but Turkey's Defence Ministry said the operation would only target militants, their bases and weapons.
The SDF said the strikes sparked "huge panic among people".
The move was triggered by Mr Trump’s announcement at the weekend that US troops would withdraw from the area, where thousands of captured ISIS fighters and their families are held by Kurdish forces.
It threatened to open a new front in the Syrian war.
But on Wednesday, Mr Trump said he did not endorse Turkey's assault on Syria, and that he expected Ankara to "abide by its commitments" to protect civilians and ensure that ISIS fighters remained captive.
He said there were no US soldiers in the area.
Mr Erdogan wrote on Twitter that the offensive was against Kurdish militants and ISIS in northern Syria, and its mission was to prevent the "creation of a terror corridor" across Turkey's southern border, and to "bring peace to the area".
The UN Security Council will on Thursday hold an emergency meeting to discuss Turkey's offensive, as requested by Belgium, France, Germany, Britain and Poland.
France, Germany and Belgium condemned the operation and NATO, of which Turkey is the second-largest army, and the EU urged restraint.
Egypt called for an emergency meeting of the Arab League.
Jean-Claude Juncker, President of the European Commission, demanded that Turkey halt its military operation, saying the bloc would not pay for its proposed "safe zone".
"I call on Turkey as well as the other actors to act with restraint and to stop the operations that are already as we are speaking under way," Mr Juncker told the European Parliament.
In Rome, hundreds of Kurdish nationals protested peacefully, carrying banners that read: “Erdogan assassin,” “America accomplice” and “Stop the occupation”.
Turkey has long been planning military action against Kurdish forces in northern Syria because of their ties with the Kurdistan Workers' Party (PKK), which has fought a bloody insurgency against the Turkish state since 1984.
In the Syrian town of Tel Abyad, people fled en masse as explosions rang out and smoke rose near by, Reuters reported.
Mr Trump's abrupt shift in Syria policy was widely criticised in Washington as a betrayal of the Kurds.
But he insisted that the move, which left the YPG vulnerable to attacks by Turkey, did not abandon the Kurds.
The Kurds, America's most effective partner in fighting ISIS in Syria, denounced the US policy shift as a "stab in the back".
The Kurdish-led civilian administration in north-eastern Syria issued a “general mobilisation” call along the border with Turkey before the assault.
“We call upon our people of all ethnic groups to move towards areas close to the border with Turkey to carry out acts of resistance during this sensitive historical time,” said the local authority, known as the Autonomous Administration of North and East Syria.
It called on the international community to live up to its responsibilities as “a humanitarian catastrophe might befall our people”.
They have warned that ISIS will use the chaos from any Turkish offensive for a resurgence and could try to break former fighters and supporters from prisons and camps where they are being held in north-eastern Syria.
The SDF said on Wednesday morning that ISIS militants had carried out suicide attacks on their positions in Raqqa, the former capital of the terrorists' "caliphate".
Mr Erdogan, due to visit Washington on November 13 at Mr Trump's invitation, on Monday said US troops had started to withdraw after a call he had with Mr Trump.
He said talks on the matter would continue.
Russia, Syrian President Bashar Al Assad's ally, said it was not told in advance about any agreement to withdraw US troops, and in a call President Vladimir Putin urged Mr Erdogan to "think carefully" before any offensive.