Two Melbourne terrorists convicted over a conspiracy to plot an attack in Melbourne's Federation Square on Christmas Day in 2016 have renounced Islamic State and their beliefs in violent extremism.

Ahmed Mohamed and Abdullah Chaarani are two of four men convicted over the plot to behead people and set off bombs, alongside brothers Hamza and Ibrahim Abbas.

"I can't say I've seen it, it's a first for me," crown prosecutor Nick Papas QC told Victoria's Supreme Court of the pair's decision to renounce their extremist views in court.

Chaarani's lawyer Patrick Tehan QC said it had only occurred in two other cases in Australia.

TERRORISTS WHO HAVE DENOUNCED EXTREMISM IN COURT:

* AHMED MOHAMED and ABDULLAH CHAARANI

Both pleaded not guilty and were convicted by a jury of conspiring to do acts in preparation for an attack in December 2016, but during their pre-sentence plea hearing both admitted their guilt.

Mohamed said he'd been swayed by Islamic State propaganda and he now hates the terror group, but he "felt like a chicken" if he had backed out of the plan.

Chaarani told the court that facing his father after his arrest had been the "most embarrassing, most humiliating" moment of his life and he now publicly renounced IS and violent extremism.

Both are due to be sentenced next month.

* MHK

A 17-year-old Melbourne boy who pleaded guilty to acts preparing for, or planning, a terrorist act over a plot to set off a homemade bomb in a crowded part of Melbourne's CBD.

He had also communicated online with a British jihadist, discussing planning and preparation for the attack.

During a pre-sentence hearing MHK said he had entirely renounced support for IS.

His initial sentence was increased on appeal to 11 years with a non-parole period of eight years and three months.

* SAMEH BAYDA and ALO-BRIDGET NAMOA

The married couple were 18 when they conspired between December 2015 and January 2016 to do acts in preparation for a terrorist attack that prosecutors said was planned for New Years Eve in Sydney.

Bayda gave evidence denying that he had renounced Islam and found Christianity to get a lighter sentence.

Namoa, who had labelled them the jihadi Bonnie and Clyde, said "I don't practise anything at the moment".

Bayda was sentenced to four years' prison and Namoa to three years and nine months. Both were immediately eligible for parole given time served.

Australian Associated Press