"United Nations humanitarian agencies have begun providing assistance directly to the most vulnerable inhabitants of Cité Soleil and other neighborhoods in the metropolitan area of Port-au-Prince, Haiti, following the recent surge in violence," the entity said via Twitter.
Nearly 300 000 people were trapped when war broke out on July 7 between the self-styled G-Pep and G-9 gangs fighting for control of the vast slum north of Port-au-Prince.
Human rights organizations said that at least 4 500 people fled the area to precarious shelters, including some 700 children without parents.
The UN says that gangs left 471 dead, wounded, and missing in Haiti in nine days. The figures refer to gang violence from July 8 to 17.
The Saint-Louis de Gonzague school in the capital, run by the Famille Kizito charity, has taken in 307 of these children, with the rest taking refuge in five other shelters.
"The humanitarian needs in Cité Soleil are immense and growing due to poverty, a lack of basis, including security, and a recent outbreak of violence," humanitarian coordinator Ulrika Richardson said in a statement.
Haiti is experiencing a severe insecurity crisis, while police forces are unable to deal with gangs fighting for control of territories.