"Justice must be served," Hollande said during a visit to Aubervilliers, located in the tough Seine-Saint-Denis region northeast of Paris.
"Justice must be served," Hollande said during a visit to Aubervilliers, located in the tough Seine-Saint-Denis region northeast of Paris where a 22-year-old youth worker, identified only as Theo, was assaulted on February 2.
But Hollande also condemned the ensuing riots, which have shaken the belt of gritty suburbs surrounding Paris.
The injuries sustained by Theo during a stop-and-search operation in the suburb of Aulnay-sous-Bois has sparked clashes with police and arson attacks across the impoverished, ethnically-mixed housing estates that ring the French capital.
The interior ministry said 245 people had been arrested over the protests which began on February 4. Several dozen have been taken into custody.
Theo suffered severe anal injuries requiring hospital treatment during his arrest by four officers, one of whom allegedly sodomised him with a truncheon.
One officer has been charged with rape and the three others with assault. All four have been suspended from the force.
On Tuesday, a separate investigation was launched into claims that one of the four officers beat up another black youth in Aulnay-sous-Bois on January 26.
The youth, also aged 22 who gave his name as Mohamed K, told L'Obs news weekly that he had been punched, kicked and beaten with a baton. Pictures published by the paper showed severe swelling and bruises to his face.
Hollande said France was determined to "show that we are capable of living together in a peaceful society, but where respect is the rule and where we must be firm towards those who diverge from this principle."
With presidential elections in April and May, the alleged assault, which follows the death of a young black man in police custody in another Paris suburb last year, has become a campaign issue.
Far-right leader Marine Le Pen on Monday launched a petition "to support the police" after blaming "laxism in French society" for the problems of the restive suburbs.
The head of the anti-immigration National Front party called for a "major tightening of the screws" to boost police capabilities.
Socialist presidential candidate Benoit Hamon lashed Le Pen, saying she was "adding fuel to the fire." "She encourages violence through her hateful rhetoric," Hamon said.
On Monday, Interior Minister Bruno Le Roux made an appeal for "responsibility, calm (and) faith in the justice system."
Hollande, who visited Theo in hospital last week, decided not to seek re-election.
The leftist Hamon, who won the Socialist nomination, is given little chance of getting past the first round on April 23.
The latest voter surveys show Le Pen with 27 percent support for the first round -- more than any other candidate -- although she is currently not expected to triumph in the May 7 runoff vote.