Local police inspector Hemant Nimbalkar said the arrests were made after several video clips were shared online showing women being attacked by men.
Police initially played down reports of sex attacks, saying they had received no official complaints.
But after viewing CCTV police officials admitted there was "credible evidence".
The attacks took place as a crowd of 10,000 gathered in the centre of the city to see in New Year on Saturday evening.
Several women described being surrounded by mobs of men before being assaulted.