Police will set up an outpost in North Melbourne on Saturday night as part of an appeal for information about the laneway sexual assault of a young mother on June 30.


Detectives from the Sexual Crimes Squad and local uniform police will set up the caravan on Victoria Street near the intersection of Chetwynd Street from 9pm until midnight and will hand out flyers along King Street and at local Nightrider bus stops and train stations, keen to speak to anyone with information about the assault.


The appeal for information comes after police arrested and questioned a 28-year-old Reservoir man over the attack. He was released pending further inquiries.


The assault, which has disturbing echoes of elements of the Jill Meagher case, involved a 23-year-old woman who was out celebrating for the first time after giving birth.


Police have CCTV footage that shows the woman, who gave birth two months ago, being dragged into Browns Lane where she was punched, kicked and sexually assaulted.


In a case described as "abhorrent" by investigators, it is believed the woman was stalked for blocks from the city to North Melbourne.


Police say she was approached by a man as she headed north from King Street about 2.45am Sunday. He tried to strike up a conversation and to hold her hand.


The woman said she was not interested and kept walking along Victoria Street and into Chetwynd Street.


Police say the attacker later grabbed her in a bear-hug then dragged her into Browns Lane where they say he punched her in the head multiple times, knocked her to the ground, kicked her and sexually assaulted her.


Detective Inspector Paul Binyon, of the sexual crime squad, said a particularly disturbing aspect of the case was that the young woman was out celebrating for the first time since the birth of her child.


"This woman did not know this man in any way. She rebuffed his advances on a number of occasions as they were walking ... it's just an abhorrent crime," he said in the days after the attack.


"Detectives are champing at the bit to identify this person and lock him up."


It is believed the woman's screams were heard by neighbours, who immediately alerted police to the assault.


The man was described at the time of attack to be of Asian or sub-continental appearance, of medium build with cropped, black hair and unshaven with stubble.


He was wearing a black top, blue jeans and an open leather jacket.


The woman's handbag was also stolen and is still missing.


A spokesman for Victoria Police urged anyone with information about the assault to immediately contact Crime Stoppers on 1800 333 000 or visit www.crimestoppers.com.au.