Terror boss welcomes US air strikes

The self-proclaimed military commander of terrorist group Islamic State says his fighters are motivated by the interventions of Western troops.

ISIS commander Omar al-Shishani (pic) has praised Sydney man and terrorist Khaled Sharrouf. (AAP)

Western air strikes against terrorist organisation Islamic State will drive more people to fight for it, the group's alleged military leader says.

Omar al-Shishani also praised Sydney man Khaled Sharrouf, a convicted terrorist wanted by Australian police for crimes in Syria and Iraq.

"He's a very loveable, good kid," al-Shishani told Fairfax radio station 3AW in an interview from Iraq.

The US on Friday began a campaign of air strikes aimed at halting the advance of militants from Islamic State (also known as ISIL or ISIS).

Al-Shishani said the intervention of Western troops had motivated his fighters and brought more Muslims to join their cause.

Already there were up to 3000 Westerners in Islamic State's ranks and more came from Europe every day.

He said they wanted the American "cry babies" to come.

"We want them to cry a little bit for their salary, cry a little bit for benefits and then come here and miss the wifey and the doggy and stuff while we slaughter them," al-Shishani said.

Islamic State proclaimed a "caliphate" straddling Syria and Iraq in late June.

Their jihad would continue until the whole world was under the rule of Allah, al-Shishani said.

Asked if this included Australia, he said: "If we can swim there, if we can catch any of your boats ... we will come to Australia."