Canberra, Oct 20 (IANS): Two Sydney schools were put on high alert on Tuesday after they received terror threats via social media.

Officers were on the scene and police are investigating the threats, Xinhua quoted a New South Wales police spokesperson as saying.

The NSW department of education put both schools under a 'lock-out' scenario where movements in and out of the schools are monitored. However, the school is functioning as normal.

"All staff and students are safe" and "both schools are working with NSW police with their investigation," a department spokesperson said in a statement.

It is believed teachers at one of the schools were asked to monitor student's behaviour last year amid fears that terrorist recruiters were targeting young people after pro-IS graffiti was sprayed over its walls.

Tuesday's lock-out comes weeks after a 15-year-old radicalised teenager executed a police accountant in an "act of terror".

It is believed a fellow school classmate, whose brother is currently facing a series of terrorism charges related to aiding and facilitating the attack, drew the 15-year-old to radicalisation.

"We need to provide more support in our schools to deal with what is a new threat," NSW Premier Mike Baird said following the attack in early October.

"This threat, that is new here, is new across the world," he said.