Prime Minister Scott Morrison has again condemned Turkey's "very concerning" behaviour in the Middle East as protesters in Sydney and Melbourne called for an end to Turkish military action in Syria.

The Sydney crowd, including families with children, stood in the rain outside Town Hall on Saturday in solidarity with Kurds affected by Turkey's incursion, which started after the United States' recent withdrawal from north-eastern Syria.

Warplanes and artillery have hit Kurdish militia targets in Syria in an offensive ordered by Turkish President Tayyip Erdogan that has killed hundreds of people, forced tens of thousands to flee and turned Washington's establishment against US President Donald Trump.

Holding aloft Kurdish flags, the crowd chanted "Shame, shame Donald Trump" and "Shame, shame Erdogan".

Earlier this week, Morrison said he had expressed "deep concern" to both the US and Turkish government's that the incursion could lead to the resurgence of Islamic State.

On Saturday, he said Turkey was "walking across borders for no other reason than that is what they seek to do for their own purposes, and Australia has condemned that".

"This is a very concerning – very concerning – act by Turkey," Morrison said in Fiji.

He said he and Foreign Minister Marise Payne had spoken with US Secretary of State Mike Pompeo, and Ms Payne had also been in contact with the Turkish ambassador.

"What we will do is continue to liaise closely with all of those who have been involved for a very long time in the co-ordinated action against Da'esh (IS) and to work with those like-minded partners," he said.

Zirian Fatah, who attended Sydney's rally with his young daughter, said the time for words was over.

The 33-year-old father-of-two, originally from Kurdistan, urged the Australian government to propose a resolution to the United Nations to impose a no-fly zone for Turkey.
Fatah, who is vice-president of the Kurdish Lobby Australia, said Mr Erdogan's actions would create a "terror corridor" which could directly affect the West.

Continued military action in the region will result in the release of thousands of IS prisoners who had been under Kurdish control, allowing them to travel anywhere in the world, he said.