Bagayoko filed a legal complaint against the CNews television channel, often described as France's Fox News, after a guest on one of its talk shows used imagery criticised as racist to comment on his election.
"The justice system needs to be much more forthright and come down hard on these acts, which are, of course, repeated offences," said the mayor from the hard-left France Unbowed party (LFI).
Prime Minister Sebastien Lecornu this week called out what he described as the "normalisation of evil and racism" following the comments against the new Saint-Denis mayor.
LFI on Thursday urged further action, reporting that several of its black lawmakers, including a deputy parliament speaker, had received a racist letter.
On Thursday night, Paris prosecutors announced that they had opened an investigation into possible public insults of a racist nature over some of the remarks broadcast on CNews.
A separate investigation had been opened into the racist abuse the mayor received on the X platform, after the comments broadcast on CNews.
More 'community policing'
Bagayoko called for the closure of CNews, arguing that the French media regulator "must be much stricter".
"Do we have to have a media landscape with racist channels like CNews and others? I say we don't," he said.
Bagayoko, a retired semi-professional basketball player, has worked for the Paris region transport authority and has been in local politics since 2001, including as deputy mayor.
He has said he grew up in a large, happy family in social housing, but also experienced discrimination and sometimes poor policing during his younger years.
Now he is in charge, he says he wants to improve life for the working-class suburb's 150,000 inhabitants, many of whom hail from waves of immigration to France, including from former colonies.
Over a third of the population in Saint-Denis live in poverty -- more than twice the national average, according to national statistics.
"The kind of policing I want is community policing, a police force that of course is capable of intervening when needed," he said, adding there would be "no cuts or reductions in frontline numbers, nor indeed any removal of cameras".
"We have 135 municipal officers, they're staying," he added, referring to the law enforcement officers under the city hall's authority.
Asked whether he wanted to disarm the municipal police, he said that he just wanted to prevent them from using any more rubber ball grenades -- sometimes used in France against protesters, and which can cause severe injuries.
He has previously said it was up to national police -- under the interior ministry -- to fight any crime linked to drug dealing in the city.
Bagayoko has replaced Mathieu Hanotin, a Socialist, who served as mayor from 2020.
