US Senate majority leader Mitch McConnell has attacked President Donald Trump's decision to pull troops from Syria as "a strategic nightmare" as scattered fighting flared in the north of the country despite a ceasefire deal.

Turkey had agreed to suspend its Syria offensive for five days but President Recep Tayyip Erdogan warned on Friday he would resume a full-scale operation against Kurdish forces if they do not withdraw from a border "safe zone."

The Kurdish-held Syrian border town of Ras al-Ain has been a major goal of the Turkish offensive since its launch on October 9 but the town's Kurdish defenders have put up fierce resistance
The Kurdish-held Syrian border town of Ras al-Ain has been a major goal of the Turkish offensive since its launch on October 9 but the town's Kurdish defenders have put up fierce resistance AFP / Ozan KOSE

Trump said Erdogan told him there had been "minor sniper and mortar fire" in the region "that was quickly eliminated" and the Turkish leader assured him in a call that "he very much wants the ceasefire, or pause, to work."

Mustefa Bali, a spokesman for the Kurdish Syrian Democratic Forces (SDF), accused Turkey, however, of violating the ceasefire deal reached during a visit to Ankara on Thursday by US Vice President Mike Pence.

A girl wounded in the Turkish offensive against Kurdish-controlled northeastern Syria lies in a hospital bed in Tal Tamr, near the flashpoint border town of Ras al-Ain
A girl wounded in the Turkish offensive against Kurdish-controlled northeastern Syria lies in a hospital bed in Tal Tamr, near the flashpoint border town of Ras al-Ain RUDAW / HO

"Despite the agreement to halt the fighting, air and artillery attacks continue to target the positions of fighters, civilian settlements and the hospital" in the border town of Ras al-Ain in northeastern Syria, he said.

McConnell on Friday said Trump's decision to withdraw US troops would help Washington's foes and hurt its allies.

"Withdrawing US forces from Syria is a grave strategic mistake," McConnell, the top Republican in Congress, wrote in The Washington Post.

Women react during the Turkish offensive against Kurdish-controlled areas of northeastern Syria in Tal Tamr, near the Syrian Kurdish town of Ras al-Ain
Women react during the Turkish offensive against Kurdish-controlled areas of northeastern Syria in Tal Tamr, near the Syrian Kurdish town of Ras al-Ain RUDAW / HO

"It will leave the American people and homeland less safe, embolden our enemies, and weaken important alliances."

The deal brokered by Pence was meant to provide a pause for the evacuation of Kurdish fighters from a "safe zone" Turkey wants to control along its border with Syria. Ankara considers the Kurdish forces to be "terrorists" linked to Kurdish rebels inside Turkey.

Map of northeastern Syria and chronology of events as of October 18.
Map of northeastern Syria and chronology of events as of October 18. AFP / Gal ROMA

"If the promises are kept until Tuesday evening, the safe zone issue will be resolved," Erdogan told reporters in Istanbul. "If it fails, the operation... will start the minute 120 hours are over."

The suspension of hostilities looked designed to help Turkey achieve its main territorial goals without fighting, but its Syrian proxies continued to clash with Kurdish fighters on Friday.

Fourteen civilians were killed in Turkish air strikes and mortar fire by allied Syrian fighters in and around the village of Bab al-Kheir, the Syrian Observatory for Human Rights said.

A woman and a child react as the body of a man killed during Turkish shelling near the Syrian Kurdish town of Ras al-Ain arrives at a hospital in the nearby town of Tal Tamr
A woman and a child react as the body of a man killed during Turkish shelling near the Syrian Kurdish town of Ras al-Ain arrives at a hospital in the nearby town of Tal Tamr AFP / Delil SOULEIMAN

The Britain-based war monitor said eight fighters of the SDF -- the de facto army of the embattled Kurdish autonomous region -- also died.

No enforcement by US troops

US Secretary of State Mike Pompeo said on Friday there was also "some very positive activity".

US President Donald Trump has been facing bipartisan criticism since he announced the US was pulling its troops out of Syria
US President Donald Trump has been facing bipartisan criticism since he announced the US was pulling its troops out of Syria AFP / Nicholas Kamm

"And we're hopeful in the hours ahead that both the Turks who were part of the agreement alongside of us as well as the YPG fighters in the region will take seriously the commitments they made," he told reporters in Brussels.

Under the deal, Kurdish forces are required to withdraw from a border strip 32 kilometres (20 miles) deep.

Pentagon chief Mark Esper said Friday that US troops were continuing their "deliberate withdrawal" from northeast Syria.

"No US ground forces will participate in the enforcement of this safe zone, however, we will remain in communication with both Turkey and the SDF," Esper said.

A senior Pentagon official said US forces would carry out aerial reconnaissance of the "safe zone" with the goal of watching over prisons holding Islamic State fighters.

Thousands of IS fighters and their family members are held in Kurdish-run jails and camps across northern Syria.

The Kurds have said hundreds of IS-linked women and children have escaped a camp, while other reports have emerged of a handful of jihadist breakouts.

The prospect of thousands of the world's most radical jihadists escaping in the chaos caused by Turkey's invasion has caused widespread alarm.

Trump said Friday that "some" European countries, which he did not name, "are now willing, for the first time, to take the (captured IS) Fighters that came from their nations."

"This is good news, but should have been done after WE captured them," he said.

'Complicated region'

The Turkish offensive was sparked by Trump's abrupt withdrawal of US troops from Syria, a move that triggered fierce bipartisan criticism in Washington.

Kurdish forces have put up fierce resistance in Ras al-Ain, with a network of tunnels, berms and trenches that held off the Turkish onslaught for a week.

The Turkish military and its Syrian proxies -- mostly Arab and Turkmen former rebels used as a ground force -- have so far seized around 120 kilometres (70 miles) of territory along the border.

More than 500 people have been killed on the two sides, including nearly 100 civilians, while around 300,000 have been displaced, according to the Observatory.

The SDF fought alongside US forces to defeat IS in Syria and Iraq, but Trump has argued that it was no longer the US' role to ensure calm in the volatile area.