An illegal immigrant from Mali has been offered French residency and a government job by President Emmanuel Macron after dramatically scaling a Paris apartment block to save a boy about to fall from a fourth-floor balcony.

Video shows Mamoudou Gassama, 22, risking his life on Sunday as he climbed up the balconies to rescue the child, clinging to a railing and glancing at the ground below, in front of horrified onlookers.

The video went viral and Mr Gassama, who has been nicknamed “spiderman” for reaching the boy in time, was swiftly granted a personal meeting with Mr Macron in a gilded room of the Elysee Palace on Tuesday morning (AEST).

“I did it because it was a child,” French newspaper Le Parisien quoted Mr Gassama as saying. “I climbed … Thank God I saved him.”

Mr Macron congratulated Mr Gassama for “an exceptional act” and said France would give him a job in the emergency services.

Mr Gassama was also awarded a medal by the rescued boy’s Paris prefecture for “courage and devotion”.

“Bravo. We’ll obviously be setting all your papers straight and if you wish it, we will start the process of naturalisation so that you can become French,” Mr Macron told Mr Gassama.

Mr Macron stressed that not all who make the treacherous journey to Europe can be welcomed, but Mr Gassama’s actions were admirable.

“You saved a child. Without you, no one knows what would have become of him,” he said.

“You need courage and the capability to do that.

“What you have done corresponds with what firefighters do; if this fits your wishes, you could join the firefighters’ corps so that you can do (such acts) on a daily basis,” he said.

Mr Gassama with his award for saving a young child hanging from a fifth-floor balcony. Photo: AAP

Mr Gassama told Mr Macron he tried to cross the Mediterranean in March 2014 to reach Italy but was caught by police.

Mr Gassama also told Paris Mayor Anne Hidalgo by phone on Sunday he arrived from Mali a few months ago and wished to stay in France.

“I replied that his heroic gesture was an example for all citizens and that the City of Paris will obviously be keen to support him in his efforts to settle in France,” Ms Hidalgo said.

The boy’s father, meanwhile, has been arrested after telling police he had left his son alone to go shopping and returned home later than planned because he was playing Pokemon Go, an enhanced reality game, on his smartphone.

“His behaviour constitutes an offence, failing to honour parental responsibilities, which carries a possible sentence of two years in jail,” a police spokesperson said.

Mr Gassama is initially being offered a spell of community service work at the Paris emergency services department.

-with AAP