Ben Roberts-Smith - Australia's most-decorated living soldier - will remain behind bars after his lawyers did not seek bail over charges of alleged war crimes in Afghanistan.

Roberts-Smith, 47, was arrested at Sydney Airport on Tuesday and charged with five counts of the war crime of murder before being transferred to a police cell.

On Wednesday, lawyers for the Victoria Cross recipient did not immediately apply for bail. Roberts-Smith denies all wrongdoing, previously calling the claims "egregious".

The criminal case comes after a defamation judgement in 2023 found the former corporal in Australia's Special Air Service Regiment (SAS) killed several unarmed Afghans between 2009 and 2012.

The years-long defamation proceedings - initiated by Roberts-Smith - marked the first time in history that any court had examined claims of war crimes by Australian forces.

Roberts-Smith's lawyers argued that the alleged killings were either legal, as they took place during combat, or did not happen at all.

Defamation cases are typically dealt with in the civil court system which requires a lower burden of proof.

The judge in the defamation case found that, on the balance of probabilities, there was substantial truth to allegations of war crimes by Roberts-Smith, who received Australia's highest military honour for bravery in 2011.

In the criminal case, Roberts-Smith faces one charge of the war crime of murder, one of jointly commissioning a murder, and three of aiding, abetting, counselling or procuring a murder. The maximum penalty for the charges is life in prison.

Earlier, the Australian Federal Police (AFP) confirmed the case had involved a complex and thorough investigation.

"It will be alleged the victims were shot by the accused or shot by subordinate members of the ADF [Australian Defence Force] in the presence of, and acting on the orders of, the accused," AFP Commissioner Krissy Barrett said on Tuesday.

She added that the allegations of misconduct were confined to a "very small section" of the ADF and that the majority of the country's armed forces "do our country proud".

Roberts-Smith is due back in court on 17 April, and will appear via a video link.