Two charged over Parramatta terror killing

Two men who allegedly helped radicalised teenager Farhad Jabar kill NSW police accountant Curtis Cheng in a terror attack have been formally charged.

A 22-year-old has been charged with three offences including supplying the gun that 15-year-old schoolboy Jabar used to kill Mr Cheng outside police headquarters in Parramatta on October 2.

He's been refused bail and is due to appear in Parramatta Local Court on Friday.

An 18-year-old man, who has been on remand since counter-terrorism raids in Sydney's west last week, has meanwhile been charged with a Commonwealth terrorism offence.

The charge, which involves aiding, abetting, counselling and procuring the commission of a terrorism act, carries a lifetime imprisonment.

He's been refused bail and is due to face Central Local Court.