French police have flooded the troubled Marseille district of La Castellane with forces since a crackdown on the drug trade started last month, and one mother told how she feels safer, for now at least.

Before, drug dealers would hang around the housing estate, and up the road, some had set up a roadblock of shopping carts and wooden pallets to keep authorities out.

"They took the carts and pallets away. Now you no longer hear the shouting, the young guys loitering," the woman said outside her son's school, refusing to give her name for fear of reprisals.

"It's a relief, especially for my 10-year-old son," she added, standing at the foot of huge white housing blocks in La Castellane.

"He looks older, so the guys would always call him over on his way to school," she said. "I was terrified they would recruit him."

President Emmanuel Macron last month announced an "XXL" cleanup of drug trafficking in the southern port city and other towns across France where the lucrative drug trade has caused death and uncertainty.

Turf wars for control of Marseille's drug dealing left 49 people dead last year. Four were innocent bystanders.

Residents of La Castellane and La Paternelle, two of the worst-hit districts, are relieved by the clampdown. But many fear insecurity will return when police leave. Almost all refused to give their names out of fear for their safety.

  'PR stunt' 

In La Castellane, a father watched his two boys play near a mural of football superstar Zinedine Zidane, who was born in the district.

"It's been calmer for three weeks," he said, before hastily adding: "Drug dealers are none of my business."

Sitting with friends outside a shop, another young man in a baseball cap said he was unimpressed.

"They came here to 'clean up', but those suffering the most are residents being slapped with fines" for car offenses, he said.

"If you see someone selling hash, you walk away, that's it," he added.

"There are more worrying things here -- the dirtiness, the rats."

Among a dozen police officers at the entrance to the neighborhood, one said certain residents would be unhappy because "some lived from" the drug trade.

Another said the clean-up had pushed dealers "elsewhere" or onto social media to make sales. Police say they have arrested around 850 people.

Authorities have promised to maintain pressure on gangs, but they will also be busy securing the city for the arrival of the Olympic torch on March 8 as part of a nationwide tour before the Paris Games this year.

One investigator, who spoke on condition of anonymity, said the clean-up operation was "a PR stunt".

"It looks good to... deploy some blue uniforms. You can see it... calm has returned for the moment," the investigator said.

"But it needs to be non-stop. And there needs to be a return to the basics... re-opening police stations in the housing estates --- not just crackdowns."

An internal investigation has since January been looking into alleged corruption among drug crime police in Marseille, according to the police and a police source. 

 'Nothing here' 

In La Paternelle, four dealing points that once generated 200,000 euros ($217,000) a day have disappeared since January as part of a police crackdown that started before Macron's announcement.

On the orange walls of a small apartment building, "menus" once advertising drugs for sale have been erased.

Just the word "Yoda" acts as a reminder of the gang that once fought for control of the area against its rival "DZ Mafia". That caused many of the drug-related deaths in the city.

Onissa, a resident who said she had lived in the neighborhood for 24 years, said the district was getting more sleep.

"No one wakes up in the middle of the night anymore," she said. "But we still are still wary."

Many people have scars from Marseille's drug battles.

Onissa said she would never forget her son's face after he saw a 35-year-old shot dead below their flat in May last year.

Not far off, two elderly women sat in the sun at the foot of an apartment block.

They recalled armed men in balaclavas suddenly appearing one afternoon in the middle of a children's playground.

One of the women sat on her walking frame in a space where youth gang members once burnt wooden pallets.

But she said she wished there were children's games on the nearby grass.

The owner of the only shop on the housing estate agreed.

"A little life is coming back, but there is nothing here," he said.