Some of the marchers reportedly came from a church in northern Seoul that was shut down after it was linked to dozens of infections.
Earlier Thursday, about 20 other activists held a similar anti-dog meat rally nearby. They bowed and laid white flowers before a framed photo of a dog in a mock funeral for the animal.
The allegations have split many in South Korea over how to remember Park Won-soon, who was found dead Friday in a wooded area in northern Seoul.
A heavyweight figure in the ruling centre-left Democratic party, Park ran South Korea's sprawling capital - home to almost a fifth of the national population - for nearly a decade.
Police say officers are looking for Mayor Park Won-sun at a Seoul site where his mobile phone signal was last detected.
At least 12 of the new cases were linked to international arrivals as the coronavirus continues to strengthen its hold elsewhere around the world.
The banner removal comes amid large US protests that began after George Floyd, died after a white Minneapolis officer pressed his knee into his neck at length as he lay face down and handcuffed.
Seoul and nearby cities restored some controls in recent weeks by shutting thousands of bars, karaoke rooms and other entertainment venues to slow the spread of the virus.
With spectators barred because of the coronavirus, FC Seoul came under fire after dozens of dolls wearing T-shirts or holding placards with the logo of a sex-toy seller appeared at Sunday's game.
After South Korean football club FC Seoul was accused of placing sex dolls in the stands, AFP Sport looks at some of the innovations:
The team will work closely on-ground with the district authorities to resolve the situation and assist with real-time remedial and rehabilitation measures.
Of the 18 new cases, 17 were linked to a 29-year-old man who visited three clubs in Seoul's Itaewon leisure district last Saturday and later tested positive.
South Korean conglomerate boss convicted of rape but given 2.5-year-jail term suspended for four years
Kim Jun-ki, the 75-year-old ex-chairman of DB Group, which has activities in finance and steel, repeatedly violated the two women, the Seoul Central District Court found.
A church official explained that only pre-registered followers were allowed to attend the service, and they were kept at least one meter apart from one another.
North Korea and South Korea leaders Kim Jong Un and Moon Jae In to meet at military demarcation line before summit
Moon will greet his visitor at the concrete blocks that mark the border between the two Koreas in the Demilitarized Zone, the chief of the South's presidential secretariat Im Jong-seok said.