French presidential frontrunner Emmanuel Macron faced a storm of criticism from his right-wing opponents over his comments condemning France's colonial past in Algeria, and on Thursday he refused to back down.

On a visit to Algiers on Tuesday Macron said France's history in Algeria was a "crime against humanity", he went on: "It's really barbaric and is part of that past that we must face up to also by apologising to those who were hurt."

Algerians lived under French rule for 132 years until it won a bloody war of independence in 1962. The conflict killed 1.5 million Algerians, the Algerian government says.

On Thursday, far-right leader Marine Le Pen, who Macron looks likely to face in a second-round run-off, said on Facebook: "Is there anything worse when you want to become president than going abroad to accuse the country you want to lead of crime against humanity?"Macron refused to back down, he said: "We must find the courage to call things by their name," he said. "Are we condemned to forever live in the shadows of this traumatic experience for our two countries?"

Polls show that Macron has a strong chance of winning the French presidency in May and his strong criticism, unusual for someone running for high office, also made the front page of daily Le Monde, with the headline: "Macron sparks controversy".

Another rival for the presidency, conservative Francois Fillon zeroed in on the row, saying in a campaign speech: "This dislike of our history, this continual repentance, is unworthy of a candidate for the presidency of the Republic."

Before winning the presidency, President Francois Hollande suggested it was time to turn the page on France's Algerian colonial history, although he stopped short of offering the formal apology many in Algeria want to hear.