Turkish President Recep Tayyip Erdogan said he would press on with an offensive into north-east Syria and "crush the heads of terrorists" if a deal with Washington on the withdrawal of Kurdish fighters from the area is not fully implemented.

Key points: Turkey's Defence Ministry said there had been 14 "provocative attacks" from Syria

Turkey's Defence Ministry said there had been 14 "provocative attacks" from Syria Kurdish militia accused Turkey of violating the truce by shelling civilian areas in the northeast

Kurdish militia accused Turkey of violating the truce by shelling civilian areas in the northeast The five-day ceasefire aims to ease humanitarian crisis and security scares over Islamic State captives guarded by the YPG

Mr Erdogan agreed on Thursday, during talks with US Vice-President Mike Pence, to a five-day pause in the offensive to allow time for the Kurdish fighters to withdraw from a "safe zone" Turkey aimed to establish in north-east Syria near the Turkish border.

On Saturday the fragile truce was holding along the border, with just a few Turkish military vehicles crossing the border, said Reuters journalists at the scene.

In the past 36 hours, there have been 14 "provocative attacks" from Syria, Turkey's Defence Ministry said, adding it was continuing to coordinate closely with Washington on implementation of the accord.

If the agreement with the United States, a NATO ally, for the Syrian Kurdish YPG militia to withdraw falters, Turkey will continue its military operation from where it left off, Mr Erdogan said.

"If it works, it works. If not, we will continue to crush the heads of the terrorists the minute the 120 hours [of the ceasefire] are over," Mr Erdogan told flag-waving supporters in the central Turkish province of Kayseri.

"If the promises that were made to us are not kept, we will not wait like we did before and we will continue the operation where it left off once the time we set has run out."

Mr Erdogan said Turkey would continue its military operation from where it left off if the deal fell through. ( AP: Presidential Press Service )

The Turkish Government regards the YPG, the main component of the Kurdish-led Syrian Democratic Forces (SDF), as a terrorist group because of its links to Kurdish insurgents in south-east Turkey.

On Friday, the Kurdish militia accused Turkey of violating the five-day pause by shelling civilian areas in the north-east and the border town of Ras al-Ain.

A senior Turkish official called the accusations an attempt to sabotage the agreement between the Turkey and the US governments.

"Turkey is 100 per cent behind the deal. We already got everything we wanted at the negotiating table," the official said.

"It's bizarre to think that we'd violate an agreement that we like."

Hundreds of thousands flee violence

The surprise deal to suspend Turkey's military offensive in Syria hinged on Mr Erdogan's demand that Washington agree on a time limit on any ceasefire, a senior Turkish official told Reuters on Friday.

The deal aims to stem a humanitarian crisis, which displaced 200,000 civilians in the region, and ease a security scare over thousands of Islamic State captives guarded by the YPG, who the Turkish assault targets.

The planned safe zone would go 32 kilometres into Syria.

Mr Erdogan said on Friday it would run for some 440 kilometres from west to east along the border, though the US special envoy for Syria said the accord covered a smaller area where Turkish forces and their Syrian rebel allies were fighting.

Mr Erdogan also said Turkey would set up a dozen observation posts across north-east Syria, and that he would hold talks with Russian President Vladimir Putin on what steps to take in the planned "safe zone" next week.

The truce also aimed to ease a crisis triggered by US President Donald Trump's abrupt decision earlier this month to withdraw all 1,000 US troops from northern Syria, a move criticised in Washington and elsewhere as a betrayal of loyal Kurdish allies who had fought for years alongside US troops against Islamic State.

It is estimated that 200,000 civilians have been displaced by the fighting. ( AP: Baderkhan Ahmad )

Mr Trump defended his decision as "strategically brilliant" and said the truce reached with Turkey would save millions of lives.

The US President later said he held a phone call with Mr Erdogan and that the Turkish leader "very much wants the ceasefire, or pause, to work".

But Mr Trump's move also means the extent of Turkey's ambitions in the region is likely to be determined by Russia and Iran, who both support Syrian President Bashar al-Assad, and look to fill the vacuum created by the US retreat.

The Syrian President has already deployed his forces in territory formerly protected by Washington, invited by the Kurds.

'We need a solution'

Mr Erdogan, who has backed rebels fighting to oust Mr Assad, has said Turkey had no problem with Syrian government forces deploying near the border.

But Mr Erdogan said on Saturday he would discuss the Syrian deployment in northern Syria in his planned talks with Mr Putin during a visit to Russia's Black Sea resort of Sochi on Tuesday.

"In certain parts of our operation area, [the Assad] regime forces under Russian protection are situated," he said.

"We will discuss this issue with Mr Putin. We need to find a solution.

"But the same is valid there too. If it works, it works. If not, then we will continue to implement our own plans."

While Mr Erdogan and Mr Putin have forged close ties over defence and energy cooperation, as well as efforts to find a political solution in Syria, Moscow has said the Turkish offensive into Syria was "unacceptable" and should be limited.

On Friday, Russian officials discussed with Mr Assad in Damascus the need to de-escalate the situation in north-east Syria, Russia's Foreign Ministry said.

Reuters