Seven teens are being questioned after their arrest in dawn raids over the "senseless" stabbing murders of two boys.
Chol Achiek, 12, and Dau Akueng, 15, died after being attacked while walking home at Cobblebank, in Melbourne's outer northwest, on September 6.
The youths were ambushed by a group of masked males armed with machetes and other bladed weapons.
Another boy walking home from a basketball game with the slain pair managed to escape.
Police raided properties in seven suburbs, all in Melbourne's outer west, northwest or north, on Thursday morning.
Homicide Squad detectives arrested seven teenagers, including a 19-year-old Thornhill Park man, a 19-year-old Caroline Springs man and an 18-year-old Wollert man.
Three 16-year-old boys and a 15-year-old boy, all from the northwestern suburbs of Melbourne, were also arrested.
Charges are yet to be laid against any of the teens.
Victoria Police Assistant Commissioner Martin O’Brien said the arrests were the result of almost two weeks of diligent and thorough police work after the tragic deaths.
"The word senseless has been used so many times already in relation to the deaths of Dau Akueng and Chol Achiek, because the reality is that it doesn’t make sense," he said.
"Two children walking home after playing sport, who should have had decades of their lives ahead of them.
"Instead, their devastated families are grieving their loss and all the things they will never get to see two children grow up to achieve and experience."
Detective Inspector Graham Banks previously said the attack had the "hallmarks of a youth gang crime".
Neither of the victims were gang members, police said.
The 15-year-old's father, Elbino Akueng, said his son "was a basketball player, not a criminal".
A GoFundMe page set up after the deaths said Dau grew up in the flats around Fitzroy and Collingwood, playing and refereeing for the Collingwood Basketball Association.
He also played for the Wolfpack Basketball Club after his family moved to the city's outer west, while Chol was a member of the Nile Warriors Basketball Club.
Chol’s father, Chuti Ngong, told mourners at a vigil his son was a peaceful boy who was loved by everybody.
CCTV footage from the scene showed a group of three males chasing a boy and attacking him on the ground, with his screams calling a woman to his aid.
The impact of boys' deaths has been felt right across the Victorian community, police said.
"I know many people will be feeling shocked, frustrated and concerned in light of this matter," Mr O’Brien said.
"I want to reassure you that locally, police will have increased patrols in the area and are working closely with community groups."
The Victorian government reconvened a South Sudanese Australian youth justice expert working group in response to the deaths.
The arrests were a "good thing" after almost two weeks of "excruciating pain" for the victim's families, Victorian minister Lily D'Ambrosio said.
"This has absolutely been a heartbreaking chapter," she told reporters.
Opposition police spokesman David Southwick said the boys' deaths should never have happened.
"(The families) need closure and the sooner that those individuals who were responsible for this face the full force of the law, the better I think it is for everybody," he said.
