Nice (France) (AFP) - Police were hunting three arson suspects on Thursday after an apartment building fire killed seven people in the southern French city of Nice, Prime Minister Gabriel Attal said.

The dead include three children – 5, 7 and 10 years old – and a 17-year-old who tried to escape by jumping from a window, they added.

The apartment is located in the low-income neighbourhood of Les Moulins, known for being a drug-dealing hub, in the west of the city.

“What happened here, this fire, is absolutely awful and revolting,” Attal told reporters at the scene, adding that “the investigation is ongoing, three individuals are being sought”.

Nice Deputy Mayor Anthony Borre had said earlier that surveillance footage showed three men wearing balaclavas in the vicinity.

The apartment was occupied by a family believed to have Comoran origins, regional prefect Hugues Moutouh said, referring to the southern African island nation.

Ten people were inside when the fire broke out and rescuers were alerted at around 2:30 am (0030 GMT) to the blaze on the seventh floor of the building.

In spite of the substantial resources deployed, “unfortunately seven people died during this fire”, firefighters said.

Neighbours hurriedly dragged mattresses in front of the building to break the fall of those jumping out of windows.

Four police were in psychological care after witnessing the scene.

Interior Minister Gerald Darmanin said on social media that the quick arrival of firefighters “probably prevented more deaths”.

- ‘Serious, barbaric’ -

Nice prosecutor Damien Martinelli said investigators were looking into a “criminal” cause for the fire.

“In light of the initial evidence, I have opened an investigation into acts of arson leading to death,” he told reporters at the scene.

Borre, Nice’s deputy mayor, said “These actions are serious, they are barbaric,” adding that he hoped for “a strong response” by the authorities once the investigation was over.

President Emmanuel Macron said he shared Nice’s “emotion” following the fire, posting on social media that his thoughts were “with the loved ones of those who died”.

The blaze probably started on the building’s second floor and spread through the staircase to higher floors, authorities said.

Rescuers said that three people were taken to hospital, one of them with life-threatening injuries after jumping from a window.

Arriving firefighters were confronted by a “raging apartment fire” on the seventh floor of the building. They carried out three aerial ladder rescues and evacuated dozens.

“There were flames in the staircase and smoke was entering under the door,” said Soibrata, a resident on the building’s fifth floor.

“I woke the children up, and called the firefighters who told us to put wet towels under the doors and go on the balcony” where they were rescued, she said.

Soibrata, who did not give her last name, and others in the building told AFP that the wait for firefighters had been much longer than the “10 minutes” Martinelli said it took for them to arrive.

Neighbours sprayed water on parasols and furniture on adjacent balconies to prevent falling burning debris from setting the rest of the building on fire, they said.

Twenty people were evacuated to a temporary shelter, with Nice Mayor Christian Estrosi saying a crisis unit would be set up to help anyone affected by the fire.