The announcement comes more than three-and-a-half years into Russia's full-scale invasion of Ukraine, with Macron and other French officials warning that Moscow risks not stopping at Ukraine's borders.

"A new national service will be introduced, gradually starting next summer," he said during a speech to troops in Varces-Allieres-et-Risset in southeastern France, almost three decades after France scrapped conscription.

But he said volunteers, mostly aged 18 to 19, would be deployed "only on national soil".

"In the event of a major crisis, parliament may authorise calling upon individuals beyond just volunteers," Macron added, and military "service would become mandatory".

"But aside from this exceptional case, this national service is a service of volunteers then selected to meet the needs of our armed forces."

He said it was inspired by fellow European countries, including Norway.

"At a time when all our European allies are making progress in the face of a threat that affects us all, France cannot remain idle," he said.

It would include 3,000 volunteers from the summer next year, then increase gradually so as to incorporate 10,000 youth into the army by 2030 and 50,000 by 2035, Macron said.