Photo: The Canadian Press

Syrians flee shelling by Turkish forces in Ras al Ayn on Wednesday.

Turkey launched airstrikes, fired artillery and began a ground offensive against Kurdish fighters in northern Syria on Wednesday after U.S. troops pulled back from the area, paving the way for an assault on forces that have long been allied with the United States.

Turkish President Recep Tayyip Erdogan announced the start of the campaign, which followed the abrupt decision Sunday by U.S. President Donald Trump to essentially abandon the Syrian Kurdish fighters, leaving them vulnerable to a Turkish offensive that was widely condemned around the world.

The decision was a major shift in U.S. policy and drew opposition from all sides at home. It also marked a stark change in rhetoric by Trump, who during a press conference in New York last year vowed to stand by the Kurds, who have been America's only allies in Syria fighting the Islamic State group . Trump said at the time that the Kurds "fought with us" and "died with us," and insisted that America would never forget.

After Erdogan announced the offensive, Trump called the operation "a bad idea." Later Wednesday, he said he didn't want to be involved in "endless, senseless wars."

In northern Syria, residents of the border areas were in a panic and got out on foot, in cars and with rickshaws piled with mattresses and a few belongings. It was a wrenchingly familiar scenario for the many who, only a few years ago, had fled the advances on their towns and villages by the Islamic State group.

Plumes of smoke could be seen rising near the town of Qamishli and clashes continued late Wednesday amid intense shelling as Turkey struck at least six different border towns along a 300-kilometre stretch. At least seven civilians and three members of the Kurdish-led force known as the Syrian Democratic Forces were killed in the Turkish bombardment, Kurdish activists and a Syria war monitor said.

Turkey's campaign, in which a NATO member rained down bombs on an area where hundreds of U.S. troops had been stationed, drew immediate criticism and calls for restraint from Europe. In his statement, Trump emphasized that there are no American soldiers in the immediate area under attack.

"Our mission is to prevent the creation of a terror corridor across our southern border, and to bring peace to the area," Erdogan said in a tweet announcing what he called "Operation Peace Spring."