A police operation is under way in a housing estate in the French city of Marseille where residents said “Kalashnikov shots” were fired “in the air”, sources close to the case said, adding there were no victims.

According to an AFP photographer on site, special forces entered the La Castellane estate, which is known for being a drug trafficking hot-spot.

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The outbreak of violence in the notorious estate, where a 25-year-old was shot dead last month in a settling of scores, comes as Prime Minister Manuel Valls is due to visit the southern port city later on Monday on a trip focused on security issues.

It was not immediately clear what sparked the shots, but Marseille has for years had a reputation as a hotbed of crime that has prompted some politicians to call for the army to be sent in to police the city’s toughest neighbourhoods.

Police say many murders in the city are linked to turf wars between multiple rival gangs battling for control of the drugs trade in the city’s poorest neighbourhoods.

The violence, they say, is aggravated by the easy availability of high-calibre weapons, with Kalashnikov automatic rifles being the murder instrument of choice.

Caroline Pozmentier, deputy mayor of Marseille, suggested the incident was part of a problem of drug trafficking in the area.

In 2013, Valls, who was then interior minister, had said that entire neighbourhoods were “abandoned to the dealers”.

Ironically, he was due to visit the city again Monday afternoon to salute the “excellent” results of measures taken over more than two years to fight crime.

According to the source close to the case, who wished to remain anonymous, residents in the La Castellane estate alerted police earlier on Monday that the shots were fired by “five to 10 people”.

Children who were in a creche in the estate were moved to a neighbouring school, according to the source.

Scuffles broke out between parents who wanted to fetch their kids and security forces, the AFP photographer added.