Istanbul - Turkey will set up a dozen observation posts across northeast Syria, President Tayyip Erdogan said on Friday, insisting that a planned “safe zone” will extend much farther than US officials said was covered under a fragile ceasefire deal.

Less than 24 hours after he agreed the five-day truce to allow Kurdish forces time to pull back from Turkey’s crossborder assault, Erdogan underlined Ankara’s ambition to establish a presence along 520km of territory inside Syria.

On the border itself shelling could be heard near the Syrian town of Ras Al Ain on Friday morning despite Thursday’s deal, and a spokesman for the Kurdish-led forces said Turkey was violating the ceasefire, hitting civilian targets in the town.

But Reuters journalists at the border said the bombardment subsided around mid-morning and a US official said most of the fighting had stopped, although it would “take time for things to completely quiet down”.

US President Donald Trump said on Friday he had spoken with Erdogan who told him there had been some “minor” sniper and mortar fire in northeastern Syria despite the truce, but that it had been quickly eliminated.

“He very much wants the ceasefire, or pause, to work,” Trump said in a post on Twitter. “Likewise, the Kurds want it, and the ultimate solution, to happen.” The United Nations Office for the Coordination of Humanitarian Affairs described the situation as “reportedly calm in most areas, with the exception of Ras al-Ain, where shelling and gunfire continued to be reported earlier today,” UN spokesman Stephane Dujarric said.

The truce, announced by US Vice President Mike Pence after talks in Ankara with Erdogan, sets out a five-day pause to let the Kurdish-led Syrian Democratic Forces (SDF) militia pull out of the Turkish “safe zone”.