Seoul Metro on Monday announced its decision to ban ads that contain "personal opinions or motivations," such as contents in favour of certain religions, ideologies and political activism -- including those by feminist organisations.
The new restriction means that such ads will not be allowed on all metro stations in Seoul and Subway Lines 1-8. Labor rights groups and feminist activists denounced the move.
The decision was made after a number of ads triggered controversy. In January, an ad that openly endorsed President Moon Jae-in was put up by his supporters on his birthday. Some citizens criticised the ad, and the Seoul Metro for allowing it, saying it damages "political impartiality" in public space.
In May, students at Sookmyung Women's University made an attempt put up an ad that protests against misogyny and spycam porn videos at the subway station named after their school, but it was disapproved by the Seoul Metro.
Last month, another group of university students filed a request to put up an ad that endorses the Panmunjeom Declaration, which was signed by President Moon Jae-in and his North Korean counterpart Kim Jong-un, in April. It was also disapproved by the authorities at the Seoul Metro.
The operator of Seoul's metropolitan railway system, however, said that ads that celebrate K-pop stars by their fans on their birthdays will continue to be allowed, as they "tend not to cause conflicts among citizens."
"It is absurd to me that just because some opinions are opposed by many, they have to be banned," said a Seoulite in her 20s who identified herself as a feminist. "What should be banned is hate speech, not legitimate opinions calling for equality."
Seoul Metro Labor Union also immediately protested the decision, saying it limits freedom of speech.
"We believe metro stations in Seoul are a wonderful space for Seoul citizens to share their opinions freely, as the city does not provide such spaces, especially for students, social minorities and civic groups," the union said in a statement.
"Instead of thinking of ways to help citizens communicate with one another better, the Seoul Metro has decided to ban all kinds of opinions altogether. They should retract the decision."
Last year, Seoul Metro announced its plan to ban all ads that promote plastic surgery clinics, especially in stations in Seoul's affluent Gangnam area, after receiving criticism that they promote lookism while exploiting women's bodies.