A woman aged 24 has been left brain dead after being shot while at home by a bullet apparently aimed at a drug dealing spot in the French Mediterranean city of Marseille, prosecutors said Monday.

The shooting Sunday raises new concerns about the effects of drug crime in Marseille, as the port city is set to host fixtures for the Rugby World Cup and a visit from Pope Francis in the coming weeks.

"Going about her life peacefully" in her mother's apartment on the third floor of a block in the city's 10th district, the young woman was brought to the hospital on Sunday evening "in very serious condition and in danger for her life", prosecutor Dominique Laurens told reporters.

Two other apartments were hit by the same burst of fire, with 23 cartridge casings from a Kalashnikov rifle found on the scene, Laurens added.

Neither of their residents -- women aged 79 and 86 -- were hurt but they were in shock, she said.

Shots were first fired around 11:00 pm in the Saint-Thys district, classed as a priority security zone.

It was "usual" to see groups of young people hanging around in the evening and there was "a drug-dealing spot" in the area, Laurens said.

"After these first blind shots, a second blind burst into the air" hit the apartment block, she added.

Police have opened an investigation into attempted murder and criminal conspiracy.

Around 40 people have been killed in drug-related violence in Marseille this year, with authorities describing the situation as a "bloodbath".

wo bystanders have already died after being hit by bullets intended for other targets, with a 43-year-old woman killed in May and a 63-year-old man in April