A series of unrelated high-profile crimes in Melbourne in the past fortnight which involved young African men have prompted Prime Minister Malcolm Turnbull to weigh-in, and forced police to defend their response.

South Sudanese and Somali community leaders believe many of those involved in serious crime are young men who have been released from prison or youth detention without support, and quickly pick up where they left off.

But they dismissed criticisms of police or the state government for their response to the issue, and urged the media not to glorify makeshift gangs such as "Apex" or "Menace to Society" that have been linked to recent offending.

"When they are released, they need to be supported, so they don't go back again," Richard Deng, a South Sudanese community spokesman, said.

"This is where the problem is.

"We want to have a structure in place to help these young men who are put in prison, released, and the next day commit crime."

Ahmed Hassan, a 21-year-old with Somali heritage and director of not-for-profit group Youth Activating Youth, said the young men allegedly involved in the offences had dented community perceptions of all Africans. They used gang names as a cry for attention, he said.

"It's not about them wanting to be gangsters. It's about them being disengaged and disadvantaged.

"They are damaging the African name, and we are trying to lift it up."

It is difficult to quantify whether youths with African heritage who commit crimes are increasingly from a smaller group of repeat offenders, as suspected by the community leaders.

But Victoria Police Deputy Commissioner Andrew Crisp said on Monday that while the number of youth offenders in the state had fallen, those offenders were committing more crime, and more serious crimes, seemingly underlining their concerns.

The offences that prompted the latest youth crime firestorm - a riotous houseparty and other incidents at Airbnb rented properties, an alleged assault on a police officer, a wild brawl and robberies in St Kilda, and the trashing of a community centre - are not as serious as the carjackings, jewellery store thefts, and aggravated burglaries that peppered the past two years.

Nevertheless, Mr Turnbull said on Monday that they represented the "failure" of the Andrews Government. He was speaking after reports federal cabinet ministers representing Victoria had approached him about the issue.

"We are very concerned at the growing gang violence and lawlessness in Victoria, in particular in Melbourne," he said.

It is not the first time he has voiced his concerns about "gang violence" in Victoria.

In June, Mr Turnbull travelled to Melbourne to announce one extra intelligence officer for the national anti-gang taskforce.

Victorian Attorney-General Martin Pakula tweeted that Mr Turnbull's latest intrusion was pathetic and a joke, and chastised him for previous "pot shots" at Labor state governments in Western Australia (regarding shark numbers) and South Australia (energy).

Minister for Trade and Investment Philip Dalidakis said the state government would work closely with police on the issue, but would ignore a "bloke who can't even put on a life vest when he is on a boat in Sydney Harbour", referring to a recent fine Mr Turnbull received for not wearing the vest.

"If Malcolm Turnbull wants to flap his gums, then of course nothing will be achieved," Mr Dalidakis said.

Mr Crisp did not wish to comment on the political wranglings, but defended the force's record on youth crime.

"We are well and truly on top of what is happening in this state around youth crime," he said.

He said that while those who commit "high-harm" crimes such as home invasions, armed robberies, serious assaults and carjackings should spend time in prison, it was clear police had to be smarter about solving the problem.

"We don't want to be locking up young people, we want to be proactive, we want to prevent crime before it happens," he said.

Sentences for young men with Sudanese or South Sudanese heritage handed down in the County Court in the past year underline the concerns of community leaders that many are committing crimes within days of being released from prison.

But others sentenced for serious offences also were found to have no criminal record.

One 20-year-old born in South Sudan who punched a man and then stomped on his head in March had 20 prior convictions dating back four years.

But another 20-year-old born in Sudan who stole about $525,000 during a jewellery store robbery in Canterbury, that he committed with at least four other men last January, had no criminal record.

The remarks of Judge Jane Campton in sentencing a man in September to two years and nine months jail for two attempted armed robberies neatly outlined the despair at the plight of many young African men.

The 22-year-old was born in a Kenyan refugee camp to Sudanese parents, the second-eldest of six children. His first offences were committed as a 16-year-old.

"I really do not know what to say to you...do you want to spend the rest of your life in jail?," Ms Campton asked the man.

After he responded 'no', she asked what was going on in his life.

"It's - it's a struggle because, um, there's - it's just a struggle for me," he responded.

"Just being a black - black, um, man and yeah, it's just a struggle. It's hard but, um, I'm still young, um."

Ms Campton implored him to take the opportunities he had been given, and stay away from alcohol.

"I mean, I don't want to keep sending you to jail.It doesn't give me any pleasure, I promise you, doing it.

"So get it over and done with and this time, when you come out, you've just got to stay away from the alcohol.

"You get involved with sport again, find some cause; find something that you're interested in."