Sydney, Oct 3 (IANS): The shooting of a civilian police employee in Sydney by a teenager was an "act of terrorism", Australian authorities said on Saturday.

"This appears to have been an act of politically motivated violence so at this stage it appears to have been an act of terrorism," Xinhua quoted Australian Prime Minister Malcolm Turnbull as saying in Melbourne.

"It is a shocking crime. It is a cold-blooded murder," Turnbull said.

The teenager of Iraqi-Kurdish decent, born in Iran, shot Cutris Cheng, a 17-year veteran in the New South Wales Police's financial department, on Friday.

"We're a long way from establishing a full picture of this man, and his exact motivations still remain a mystery to us," New South Wales police commissioner Andrew Scipione said.

Initial investigations by Australian counter-terrorism authorities indicated the teenage gunman was a "clean skin" -- not on authorities radar of those suspected to be inclined toward terrorism, The Guardian Australia reported.

"We are exploring every avenue with regard to why he did what he did," Scipione said.

New South Wales Premier Mike Baird said the shooting would "echo around the world, as people try and understand how someone so young could commit such a crime."

Turnbull echoed Baird's sentiment, urging Australians to go "about their day" on Australia's "grand final weekend", where the champions are decided for two of Australia's most popular sports -- football and rugby.

The state and federal agencies are working closely together to ensure Australia's security, Turnbull said.

In December 2014, Iranian-born extremist Man Haron Monis and two hostages were killed following a 17-hour siege at a cafe in downtown Sydney.