Three Islamic State supporters who torched a Melbourne mosque to terrorise the Shia Muslim community have been jailed for more than 16 years, with a judge saying their crimes were motivated by hatred, intolerance and malevolence.

Key points: The mosque, in Melbourne's northern suburbs, had to be demolished after the men set it on fire

The mosque, in Melbourne's northern suburbs, had to be demolished after the men set it on fire Abdullah Chaarani and Ahmed Mohammed were sentenced to at least 17 years' jail

Abdullah Chaarani and Ahmed Mohammed were sentenced to at least 17 years' jail Hatim Moukhaiber was sentenced to at least 12 years' jail for his "enthusiastic" involvement

Abdullah Chaarani, 28, Ahmed Mohammed, 26, and Hatim Moukhaiber, 30, were sentenced in the Victorian Supreme Court for engaging in a terrorist act by setting the Fawkner mosque on fire in December 2016.

Last year two of the men, Chaarani and Mohammed, were also convicted over a thwarted plot to carry out a terrorist attack in Federation Square, planned for just weeks after the attack on the mosque.

The three men were captured on security footage breaking into the Imam Ali Islamic Centre during the night, and using 20 litres of petrol and a car tyre to set fire to the men's prayer section.

The fire caused $1.5 million in damage and the mosque had to be demolished.

In sentencing the men for the mosque attack, Supreme Court Justice Andrew Tinney said the Sunni Muslims had carried out a heinous crime to strike a blow against and terrorise the Shia community, which used the mosque.

Justice Tinney said it was "an attack on religious freedom" that was "impossible to excuse".

He said he was left in no doubt that the trio supported "the evil ideology" of the Islamic State (IS) group.

The men left their mark on the walls, using spray paint to write words linked to IS in English and Arabic, a message the judge said was left "for the whole world to see".

Chaarani sprayed graffiti on the mosque after it was set alight. ( ABC News )

'Shocking and evil views'

The men, who were jovial and chatty ahead of the sentence, also laughed in the dock as the judge described text messages they sent congratulating each other after the fire, one of which said "I could kiss your dick bro".

The court heard Chaarani and Mohammed had also previously tried to burn down the Islamic centre a month earlier.

Chaarani and Mohammed were sentenced to 22 years with non-parole periods of 17 years for the mosque attack and the earlier attempt in November, 2016.

Moukhaiber was sentenced to 16 years' jail, to serve a minimum of 12 years before being eligible for parole.

While Moukhaiber had not been involved in the earlier attempt, the judge said he was a "fully committed and enthusiastic member of the team" and his future rehabilitation prospects were grim if he continued to hold his "shocking and evil views".

Court rejects suggestions men had reformed

Chaarani and Mohammed made "last-minute" attempts to renounce their radical IS beliefs during a pre-sentencing hearing in late June.

Lawyers for the pair submitted documents to the court saying they had embraced deradicalisation.

Security cameras captured the men arriving at the Shia mosque in Fawkner carrying a fuel container. ( ABC News: Rudy De Santis )

Chaarani submitted numerous letters to the court — including an apology to the mosque members.

"He renounces before this court, and the public at large, the ideology of ISIS," Chaarani's defence lawyer Patrick Tehan QC told the court.

"He sees the crime … as heinous and wrong … and appreciates the suffering he caused to the mosque community."

Chaarani also wrote a letter of apology to Justice Tinney for an outburst in the court after the jury verdict was handed down in May.

But Justice Tinney questioned the "self-serving material at the last minute", with Chaarani having been charged two years ago, found guilty of the Federation Square plot in October and the mosque attack in early May.

"It seems to me up until that time and incorporating that time there was nothing that occurred in any conduct of your client that would have suggested the prospect and possibility that he was well on the path to deradicalisation," Justice Tinney said.

"If there was any truth to this material it would have reared its head sooner than now."

Chaarani expressed remorse about "the loss of his liberty", not the crime he committed, Mr Nicholson said.

Family members, friends and a large group of counter-terrorism police were in court for the sentence.