A small group of women took to the underground on Sunday with their faces covered and holding signs reading: "I can be flirtatious but you can't harass" and "We want to feel cool! We want no dirty hands!"
"We believe women have the freedom to choose what to wear how people dress should never be an excuse for sexual harassment," one of the protesters, whose online name is Xiangqi, told the China Daily newspaper.
The protest was triggered by an online message posted by the Shanghai metro authorities last week counselling female passengers to dress more discreetly. "Girls, please be self-dignified to avoid perverts," it said.
The post, which was accompanied by a photograph of a woman waiting for a train wearing in see-through dress, followed a spate of sexual crimes on Shanghai's sprawling underground system.
Earlier this month police announced a crackdown on metro "harassers" after arresting 3 men for flashing and assaulting female passengers in the space of seven days.
The most recent attack came at rush hour last Tuesday when a man reportedly "exposed" himself to a female passenger on a packed commuter train.
One witness told the Shanghai Daily the victim had shouted: "What's that down below? How sick you are! How can you be called a man? Catch him!" The man was subsequently caught and beaten by passengers before being led away in tears by police.
One week earlier police arrested another man accused of ejaculating on a woman's legs while on a train at the People's Square Station, a popular sightseeing destination.
Lan Tian, a media officer from the Shanghai Metro operations centre, defended the online warning saying it was intended as "a kind reminder for more self-protection".
He described reports of a protest on the underground as "sheer hype", blaming it on a "feminist organisation."
Asked why the offending message had not been taken down despite widespread criticism, Mr Lan said: "We feel obliged to remind female passengers about self-protection and they are free to wear fewer clothes. There is no conflict between these two things."
Mr Lan rejected calls for the introduction of female-only carriages, like those in Mexico City, Tokyo and Rio de Janeiro.
"For one thing, we don't have many perverts. Secondly, we have to deal with the passenger flow and transport capacity." After 3-decades of breakneck growth, Shanghai now has the most extensive underground network on earth with around 260 miles of track serving this mega-city of some 23m people.