The pope’s forceful interventions come as the migration debate has been stoked by mass arrivals on the Italian island of Lampedusa last week.
Speaking at a monument to people lost at sea on his arrival in Marseille on Friday, the pontiff had insisted that “people who are at risk of drowning when abandoned on the waves must be rescued.”
He thanked aid groups rescuing migrants in danger at sea, condemning efforts to prevent their work as “gestures of hate”.
Around 40 people have been killed in shootings in Marseille this year, and Macron has promised billions of euros to upgrade city infrastructure in a bid to stop the downward spiral.
Not everyone has welcomed the pope’s visit.
Some politicians on the left have criticised Macron’s decision to attend Saturday’s mass as an infringement of state secularism. Others on the right have attacked Francis for “interfering” in domestic politics.