US President Donald Trump on Monday again blamed immigration for protests and violence that have rocked France in recent days, urging Europe and French President Emmanuel Macron to tighten borders.

"What's happening in France has to do with immigration, not schools, not anything," Trump told reporters in Washington, echoing his comments from the day before. "It's immigration, and I told President Emmanuel Macron, close up your borders."

Weekend demonstrations over soaring prices were held in Paris and other cities, degenerating into some of the worst street violence France has seen in recent years.

Trump recounted a conversation with Macron, telling him "a long time ago, you're making a big mistake in France. You're letting everybody from the world come in. The whole world was coming in.

"Paris is going to be a Muslim city very soon," the 80-year-old Republican added.

"If Europe doesn't close its borders and bring the criminals out, like the people that are protesting, Europe is finished."

Trump made combating illegal immigration a central pledge of his 2024 campaign, at times relying on false claims that played on racial fears.