War hero Ben Roberts-Smith arrested over Afghan murder charges

Former Australian SAS soldier Ben Roberts-Smith has been arrested at Sydney airport and is expected to face five counts of murder over alleged war crimes in Afghanistan.

The 47-year-old Victoria Cross recipient was taken into custody on Tuesday following a lengthy investigation by the Office of the Special Investigator into alleged killings of unarmed Afghan civilians during deployments between 2009 and 2012.

The AFP confirmed a former ADF member was expected to be charged with five counts of war crimes involving murder — carrying a maximum penalty of life in prison.

Roberts-Smith is also accused of aiding, abetting, counselling or procuring others to commit murder on three separate occasions. He is expected to appear in a NSW court later Tuesday.

The arrest follows a landmark Federal Court defamation judgment in which Justice Anthony Besanko found on the balance of probabilities that Roberts-Smith had machine-gunned an unarmed prisoner during a 2009 raid, taking the man's prosthetic leg back to Australia as a drinking vessel.

Justice Besanko also found Roberts-Smith had kicked a handcuffed man, Ali Jan, from a 10-metre cliff before ensuring he was shot dead, and had stood by while a rookie soldier was ordered to execute an elderly Afghan prisoner to be "blooded."

The criminal standard of proof beyond reasonable doubt is significantly higher than the civil findings made in that defamation case.

Roberts-Smith has maintained his innocence.