Donald Trump has blasted the Turkish assault on Syrian Kurds and ISIS fighters, saying he 'does not endorse' President Erdogan's long-awaited military assault in Syria today.

Turkish leader Recep Tayyip Erdogan announced the start of the offensive - called 'Operation Peace Spring' - on Wednesday afternoon, and soon after, jets and artillery bombarded Kurdish positions along the border - sending thousands of civilians fleeing.

The intensive shelling paved the way for Turkish troops to start crossing the Syrian border on Wednesday evening.

Trump - who ordered American troops out of the area - said Turkey's incursion into the area was a 'bad idea' and said that Washington 'does not endorse this attack.'

In the statement, Trump added that Turkey had committed to 'ensuring no humanitarian crisis takes place - and we will hold them to this commitment.'

The Kurdish-led Syrian Democratic Forces (SDF) said Turkish warplanes had caused 'huge panic' when they attacked the Kurdish-held territory today, and have claimed the bombing has killed five civilians and wounded others.

SDF spokesman Mustafa Bali said on Twitter: 'Turkish warplanes have started to carry out air strikes on civilian areas.'

Pictures and video footage from the ground appeared to show civilians desperately fleeing the area as clouds of smoke rose from the positions targeted by Turkish jets. 

There were signs of panic in the streets of Ras al-Ayn- one of the Syrian towns under attack with residential areas close to the borders.