U.N. spokeswoman Michele Montas in New York said the Uruguayan CASA212 aircraft went down in rugged terrain west of Fonds-Verrettes near the border with the Dominican Republic, some 28 miles from the capital, Port-au-Prince.
"The aircraft was on a regular reconnaissance flight," Montas said in a statement.
Rescue teams had to reach the area by foot because there were no roads nearby, and they found no survivors, she said.
U.N. police were guarding the crash site, where all bodies were recovered and would be taken back to the capital of Port-au-Prince, according to a statement from the U.N. peacekeeping mission in Haiti.
U.N. Secretary-General Ban Ki-moon "extends his heartfelt condolences to the family members, friends and colleagues of these brave peacekeepers who lost their lives in the service of peace," Montas said.
Dozens of U.N. vehicles were parked late Friday near the main highway that connects Port-au-Prince to the Dominican border, unable to get any closer to the crash site, which is in the Ganthier municipality.
Haitian police officer David Charles told The Associated Press that personnel from his convoy walked about two hours up the mountain but was not able to reach the crash site because it was on the other side of a ridge and a river.
Charles said he saw the white plane in the distance and a large piece had broken off.
U.N. ambulances headed back to their bases late Friday, with one driver saying they had been ordered to return Saturday morning.
The victims were Uruguayan and Jordanian military personnel serving with the 9,000-strong U.N. peacekeeping force that has been in Haiti since a 2004 rebellion ousted former President Jean-Bertrand Aristide, Montas said.
The United Nations has began an investigation into the crash, Montas said.
It was unclear why the plane was doing surveillance near the border or how often such surveillance flights take place. The U.N. peacekeeping mission did not immediately respond to a request for comment.