PARIS — President Emmanuel Macron says the French government itself ­fueled homegrown Islamic extremism by abandoning its poorest neighborhoods — and he’s promising tough and ‘‘sometimes authoritarian’’ new measures to combat radicalization.

Macron unveiled a multi-billion-euro plan Tuesday to help France’s troubled ­banlieues — suburban regions where crime flourishes and job opportunities are scant, especially for minorities with origins in former French colonies.

More than 5 million people live in France’s poorest neighborhoods, where unemployment is 25 percent, well above the nearly 10 percent national average. For those under 30, the prospects are even worse. More than a third are unemployed.

Macron’s answer is to provide grants for poor youths to launch startups, double the funding for public housing, expand child care, improve public transport in isolated or poor neighborhoods, offer subsidies for companies that hire disadvantaged youth, and hire more local police officers.

Macron’s predecessors also spent billions to try to fix the banlieues, and failed. But he’s undeterred, and he says the stakes are increasingly high.

‘‘Radicalization took root because the state checked out’’ and abdicated its responsibilities in impoverished neighborhoods, Macron said.

Radical recruiters argued: ‘‘I will take care of your children, I will take care of your parents. I will propose the help that the nation is no longer offering,’’ Macron said.

Several extremist attackers who have targeted France in recent years were raised in French social housing.

ASSOCIATED PRESS