PM to speak to Turkey about Aust fighters

Prime Minister Tony Abbott will speak with the Turkish government about a crackdown on Australians crossing its border into Syria to fight with extremist groups.

Mr Abbott wants to stop people who "pretending to go to Turkey" while really planning to travel to Syria to fight with Islamic State.

"It is absolutely critical that as far as humanly possible we stop gullible, impressionable, young Australians going to places where they could very easily be killed," he told reporters in Wellington on Monday.