Officials say several gang members have been killed in a major police operation in Port-au-Prince.
Guatemala sends 150 soldiers to Haiti's capital to help a UN-backed force tackle powerful armed gangs.
Two journalists and a police officer are reported to have been killed, with others injured in the attack.
A gang leader reportedly ordered the killings after his son came down with a "mystery illness".
The charity acts after an attack on its staff in the capital and the alleged killing of two patients by police.
Tens of thousands of people have been forced to flee from months of widespread gang violence in Haiti.
Unicef says six out of 10 hospitals in Haiti are barely operational, putting millions of children at risk.
Provides an overview of Haiti, including key events and facts about this Caribbean country.
A single commercial flight left the capital Port-au-Prince on Monday and later landed in Florida.
