Clashes between police and gangs killed at least three officers in Petion-Ville, police said on Saturday.
The National Police called for calm and said it would make all "necessary efforts" to fight the country's powerful gangs.
"A police patrol was ambushed by a gang on Friday morning, " Lionel Lazarre said.
The officers called for backup but were angered because reinforcements never arrived, he added.
In addition to the officers who died, another went missing, with one officer also
seriously injured in the ambush, according to police officials.