The murders - both of 17-year-old boys - took place on Wednesday night, one in eastern Paris's 20th arrondissement, the other in Sarcelles, in the northern suburbs.
Although the killer in the Paris fight has yet to be identified, three youths, aged between 17 and 20, have been charged with gang violence.
Two of them also face weapons-related charges, while one is accused of providing a false identity to the police.
Another trio, aged between 15 and 16, have been charged with murder in relation to the Sarcelles violence.
Police in that case say they have yet to establish a motive but that it is unrelated to a recent rise in gang warfare.
According to France Info radio, the victim had accused his assailants of a rape in the area three weeks before.
Deaths rise in 2018
The Paris city murder was clearly a case of gang warfare, involving a group from neighbouring arrondissements in the poorer parts of the city.
On Thursday Interior Minister Christophe Castaner visited the 20th arrondissement and vowed to crack down on gang violence, which has led to about 10 deaths across the country this year, compared to just one in 2017.
A 13-year-old boy was murdered in a fight in Lilas, just to the east of the Paris ringroad, last week, and three other teenagers have been killed in the Paris region since the beginning of the year.
Weapons used include a cordless drill, baseball bats, teargas canisters, knives, hatchets, iron bars and pieces of furniture.
A total of 159 clashes between gangs have been recorded in France this year, according to Le Parisien newspaper, a slight rise on the previous year but with more deadly consequences.
Admitting that he could not explain why the phenomenon is growing, public prosecutor François Molins declared, "To me it's completely irrational."
Gang warfare is not new to France, Paris's "Apaches" were notorious in the early 20th century and there have been periodic eruptions, most notably in Paris and Marseille, since then.
Today social media provide a means to organise fights but that does not explain the latest rise in killings, according to police.
Nor are the gangs associated with drug-trafficking, which has given rise to turf wars, notably in the southern city of Marseille.
Two other attacks in the Paris region this weekend show the hallmarks of that sort of violence - a 43-year-old man was stabbed to death at the foot of the building where he lived after responding to a phone call and a man was shot in the legs from a vehicle in a usually calm residential area.
He was injured but his life was not in danger, according to the hospital where he was taken.