President Francois Hollande speaks of "a problem with Islam" in French society, in excerpts published on Wednesday of a book in which he also suggests that immigration needs to be curbed.

"There is a problem with Islam because Islam requires (holy) sites and recognition," Hollande told two journalists from Le Monde newspaper for the book which will be published on Thursday.

"It's not Islam that poses a problem in the sense of its being a religion that is dangerous in itself, but because it wants to assert itself as a religion in the (French) republic," he is quoted as saying in "Un president ne devrait

pas dire ca", which translates as "A president shouldn't say this".

Elsewhere in the book, Hollande says he thinks "there are too many arrivals, immigration that should not take place."

Immigration and national identity are key themes in campaigning for next year's presidential election, which has echoes of the US race for the White House, with far-right leader Marine Le Pen riding high in the polls.

A string of jihadist attacks in France in the past two years, coupled with the Europe-wide migrant crisis, have stoked anti-immigration sentiment.

A heated debate about Muslim integration in staunchly secular France came to a head over the summer when around 30 towns banned the body-concealing burkini swimsuit.