The far-right candidate in France's presidential election, Marine Le Pen, has demanded the closure of all Islamist mosques in the wake of a deadly attack on police in Paris.

She's also calling for the deportation of hate preachers, saying the attack is proof that a radical response is needed.

"The hate preachers must be expelled, the Islamist mosques must be closed," she said.

One officer was killed and two others were wounded in the attack, which took place in the build-up to the presidential election in France.

CNN's Hala Gorani explained that the shooter had previously come to the attention of French police.

"He was detained briefly in January of this year; there were reports that he was looking for weapons in order to commit crimes against police officers [and] that he had made that known"

Despite this, Police say he'd done nothing to raise suspicion that he had been radicalised.