The Haitian military deposed Aristide in 1991
The French news agency AFP quoted presidential spokesman Mario Dupuy as saying that the attacks constituted a coup attempt by ex-army officers.
Prisoners in Petionville jail, in the suburbs of the capital Port-au-Prince, were forced to shout "Long live the army" in the first assault, in which no one was injured or released.
Hours later, men in camouflage uniforms stormed a police academy that was once used to train the now-disbanded Haitian army, killing three officers.
There were reports that a police station in Mirebalais 40km north of the capital was also attacked. Local media said another policeman was killed and three abducted in this incident.
The attacks triggered protests in the capital, with supporters of President Jean-Bertrand Aristide blocking streets and burning tires.
Military grudge
There are signs all three attacks were carried out by the same people, a group of ex-army officers.
President Aristide - who was deposed in a military coup in 1991 - disbanded the army when he was returned to power with US help in 1994.
They were replaced with a civilian police force.
Nearly 1,000 former military personnel marched through the streets of the capital Port-au-Prince in the spring of this year, calling for the reintroduction of the armed forces.
Assault
In the assault on the police academy, the attackers arrived in all-terrain vehicles and sprayed dormitories with bullets.
They seized senior officer Eddy Cantave and forced him to take them to a compound where heavy arms are stored.
He was found shot dead with his hands bound. It is not known if the attackers took weapons from the compound.
A trainee and an officer on duty were also killed, and four others were lightly injured.