Thursday's attack has been compared to a gang rape last December that sparked nationwide protests and saw the country revise its rape laws.
Last night, Indian police arrested a third man in connection with the attack, which saw the woman's colleague tied up and beaten before five men assaulted her.
News of the gang rape sparked street protests and uproar in parliament, putting the spotlight back on women's safety in India, where memories of the rape and murder of a student on a bus in New Delhi last December are still fresh.
Many Indians have questioned whether, despite the toughening of rape laws, India is any safer. The latest assault was in the financial capital, Mumbai, which is generally considered India's safest city for women.
Bharatkumar Raut, a Mumbai-born lawmaker in the upper house of parliament, expressed concern that the city is becoming less secure for residents of both genders.
He said: "In the 21st century, I am ashamed that a journalist doing her job has to go through something like this.
"We used to say that Mumbai is the safest city in India. But the life of our citizens, not just women, is becoming insecure."
The 22-year-old photojournalist was admitted to hospital, where she was last night said to be in a stable condition.
Police have released sketches of the suspects and say they will ask the government to have the case conducted in a fast-track court.
Mumbai Police Commissioner Satyapal Singh said of the second suspect: "He has admitted that he has done wrong,"
The attack took place shortly before sunset in a former industrial district that is now one of the city's fastest-growing neighbourhoods.
The woman was at an abandoned textile mill on assignment with a male colleague who was helping carry camera equipment. She was working as an intern with a Mumbai-based English magazine.
They were separated by the attackers; the woman's colleague was tied up with a belt while she was assaulted.
On hearing of the attack, Nirmala Sitharaman of India's main opposition Bharatiya Janata Party wrote on Twitter: "Despicable! We are shamed! How long and God forbid, how many more before the criminals are punished? Wake up, India!"
Indian TV news channels and newspapers, citing police sources and statements said to have been made by the victim, have disclosed some details of the assault.
According to the Mumbai daily paper Mid Day, the attackers threatened to slash the victim with a broken beer bottle. They also threatened to reveal her identity if she reported the incident, it reported.
The Times of India on Saturday quoted a statement by the victim from her hospital bed.
"I want no other woman in this city and country to go through such brutal physical humiliation," she was quoted as saying. "The perpetrators should be punished severely as they have ruined my life."
Himanshu Roy, Mumbai's joint commissioner of police, declined to comment when contacted.
The trials of the four men and one juvenile accused of the December attack are expected to conclude within three weeks. Closing arguments in the trial of the four adult suspects started on Thursday.
Following a public outcry over the New Delhi attack, India introduced tougher rape laws in March, which include the death penalty being available for repeat offenders and for those whose victims were left in a "vegetative state".