Media reports have indicated that smokers will face a 90-dollar fine if they light up at Seoul's main squares, which are popular with tourists.
Under toughened anti-tobacco rules, smoking will be banned from three main squares including Seoul Plaza, Cheongyecheon Plaza and Gwanghwamun Plaza, Yonhap news agency said, quoting the city council.
Following a three-month grace period ending June 1 those who smoke in the prohibited area will be slapped with a fine of 100,000 won ($90), it said.
Seoul city also plans to designate a total of 321 public spaces as non-smoking areas by the end of December, including parks and bus stations.
South Korea's national parliament has passed a law calling on provincial governments to make it more difficult for people to smoke in public places.