Turkish ground forces pressed their advance against Kurdish fighters in northern Syria on Thursday, Turkey's Defense Ministry said, launching airstrikes and unleashing artillery shelling on Syrian towns and villages the length of its border.

The Turkish invasion, now in its second day, has been widely condemned around the world. In northern Syria, residents of the border areas scrambled in panic on Wednesday as they tried to get 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.

A Kurdish-led group and Syrian activists claimed Thursday that despite the heavy barrage, Turkish troops had not made much progress on several fronts they had opened over the past hours. But their claims could not be independently verified and the situation on the ground was difficult to assess.

Turkey began its offensive in northern Syria on Wednesday against Kurdish fighters with airstrikes and artillery shelling, before ground troops began crossing the border later in the day. U.S. troops pulled back from the area, paving the way for Turkey's assault on Syrian Kurdish forces.

Turkey has long threatened to attack the Kurdish fighters whom Ankara considers terrorists allied with a Kurdish insurgency in Turkey. Expectations of an invasion increased after President Donald Trump's abrupt decision Sunday to essentially abandon the Syrian Kurdish fighters, leaving them vulnerable to a Turkish offensive.

The Kurds, who have been America's only allies in Syria fighting the Islamic State group, stopped on Thursday all their operations against the IS extremists in order to focus on fighting advancing Turkish troops, Kurdish and U.S. officials said.

The Turkish Defense Ministry statement Thursday did not provide further details on the offensive but shared a brief video of commandos in action. The ministry said Turkish jets and artillery had struck 181 targets east of the Euphrates River in Syria since the incursion started.

Mustafa Bali, a spokesman for the Kurdish-led Syrian Democratic Forces, said their fighters have repelled Turkish forces ground attacks.

"No advance as of now,'' he tweeted Thursday.

The Britain-based Syrian Observatory for Human Rights, a war monitor that has activists throughout the country, said Turkish troops tried to push ahead on several fronts under the cover of airstrikes and artillery shelling but made no tangible progress. The Observatory said that since Turkey began its operation, seven civilians have been killed.

Turkey says it intends to create a "safe zone'' that would push the Kurdish militia away from its border and eventually allow the repatriation of up to 2 million Syrian refugees in the area.

Trump's decision to have American troops step aside in northeastern Syria 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 IS.

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.''

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.

Australia on Thursday expressed concerns the Turkish incursion could galvanize a resurgence of the Islamic State group and refused to endorse the close ally U.S. for pulling back its troops from the area. Prime Minister Scott Morrison said he had been in contact with the Turkish and U.S. governments overnight and admitted to being worried about the situation.

In Washington, officials said Wednesday that two British militants believed to be part of an Islamic State cell that beheaded hostages had been moved out of a detention center in Syria and were in U.S. custody.

The two, El Shafee Elsheikh and Alexanda Amon Kotey, along with other British jihadis allegedly made up the IS cell nicknamed "The Beatles'' by surviving captives because of their English accents. In 2014 and 2015, the militants held more than 20 Western hostages in Syria and tortured many of them.

The group beheaded seven American, British and Japanese journalists and aid workers and a group of Syrian soldiers, boasting of the butchery in videos released to the world.