Young rioters clashed with police and looted stores in a fourth day of violence in France triggered by the deadly police shooting of a teen, piling more pressure on President Emmanuel Macron after he appealed to parents to keep children off the streets and blamed social media for fuelling unrest.

Despite repeated government appeals for calm and stiffer policing, Friday saw brazen daylight violence, too. An Apple store was looted in the eastern city of Strasbourg, where police fired tear gas, and the windows of a fast-food outlet were smashed in a Paris-area shopping mall, where officers repelled people trying to break into a shuttered store, authorities said.

The southern port city of Marseille, initially spared the violence that broke out first in the Paris region, was experiencing its second night of upheaval. Even before nightfall, young people hurled projectiles, set fires, and looted shops, police said. They made almost 90 arrests.

On Friday evening, looters broke into a Marseille gun shop and made off with weapons, and a man was later arrested with a hunting rifle, police said. The previous night, two off-duty officers suffered serious injuries, including one who was stabbed, when they were set upon by about 20 people, police said.

Authorities in the city of Lyon reported rioters again setting fires and pelting police in the suburbs. In the city centre, police made 21 arrests to stop the attempted looting of shops after an unauthorized protest against police violence that drew about 1,300 people Friday evening.

Violence was also erupting in some of France's territories overseas.

In French Guiana, a 54-year-old was killed by a stray bullet Thursday night when rioters fired at police in the capital, Cayenne, authorities said. On the small Indian Ocean island of Reunion, protesters set garbage bins ablaze, threw projectiles at police, and damaged cars and buildings, officials said. Some 150 officers were deployed there Friday night.

In the face of the escalating crisis that hundreds of arrests and massive police deployments have failed to quell, Macron held off on declaring a state of emergency, an option that was used in similar circumstances in 2005.

Instead, his government ratcheted up its law enforcement response. Already massively beefed-up police forces were boosted by another 5,000 officers for Friday night, increasing the number to 45,000 overall, the interior minister said. Some were called back from vacation. The minister, Gerald Darmanin, said police made 917 arrests on Thursday alone and noted their young age — 17 on average. He said more than 300 police officers and firefighters have been injured.

Darmanin also ordered a nationwide nighttime shutdown of all public buses and trams, which have been among rioters' targets.

And he said he had delivered a warning to social networks that they can't allow themselves to be used as channels for calls to violence.

“They were very cooperative. We'll see tonight if they really are. We are going to give them as much information as possible” so that, in return, French authorities get the identities of people who incite violence, the minister explained.

“We will pursue every person who uses these social networks to commit violent acts,” he said. “And we will take all necessary measures if we become aware that social networks, whoever they are, don't respect the law.”

Macron, too, zeroed in on social media platforms that have relayed dramatic images of vandalism and cars and buildings being torched, saying they are playing a “considerable role” in the violence. Singling out Snapchat and TikTok, he said they were being used to organize unrest and serving as conduits for copycat violence.

Macron said his government would work with technology companies to establish procedures for “the removal of the most sensitive content,” adding that he expected “a spirit of responsibility” from them.

Snapchat spokesperson Rachel Racusen said the company has increased its moderation since Tuesday to detect and act on content related to the rioting.

The violence comes just over a year before Paris and other French cities are due to host 10,500 Olympians and millions of visitors for the summer Olympic Games. Paris 2024 organizers said they are closely monitoring the situation and that preparations for the Olympics continue.

The fatal shooting of the 17-year-old, who has only been identified by his first name, Nahel, was captured on video, shocking France and stirring up long-simmering tensions between police and young people in housing projects and disadvantaged neighborhoods.

Macron said a third of the individuals arrested Thursday night were “young people, sometimes very young," and that “it's the parents' responsibility” to keep their children at home.

Nanterre prosecutor Pascal Prache said officers tried to pull Nahel over because he looked so young and was driving a Mercedes with Polish license plates in a bus lane. He allegedly ran a red light to avoid being stopped and then got stuck in traffic.

The police officer accused of pulling the trigger was handed a preliminary charge of voluntary homicide after Prache said his initial investigation led him to conclude that the officer's use of his weapon wasn't legally justified. Preliminary charges mean investigating magistrates strongly suspect wrongdoing but need to investigate more before sending a case to trial.

The officer said he feared he and his colleague or someone else could be hit by the car as Nahel attempted to flee, according to the prosecutor.

Nahel's mother, identified as Mounia M, told France 5 television that she was angry at the officer but not at the police in general. “He saw a little Arab-looking kid, he wanted to take his life,” she said, adding that justice should be “very firm.”

“A police officer cannot take his gun and fire at our children, take our children's lives,” she said.

Deadly use of firearms is less common in France than in the United States, although 13 people who didn't comply with traffic stops were fatally shot by French police last year. This year, another three people, including Nahel, died under similar circumstances. The deaths have prompted demands for more accountability in France, which also saw racial justice protests after George Floyd's killing by police in Minnesota.

Nahel's burial is scheduled for Saturday, according to Nanterre Mayor Patrick Jarry, who said France needs to “push for changes” in disadvantaged neighbourhoods.