Haiti's police and the United Nations Stabilizing Mission in Haiti (Minustah) on Sunday ordered a curfew starting at 6 p.m. local time in Haiti's earthquake-hit capital Port-au-Prince.
The measure means that none can walk the streets except police or military officers or residents under escort by security forces.
Helicopters are also barred from making over-flights from 6:22 p.m. onwards.
Port-au-Prince is in darkness since Tuesday, an earthquake measuring 7.3 on the Richter scale struck around 30 kilometers outside the capital, destroying infrastructure, including power stations.
A desperate population has been driven to looting because of a shortage of food and water, as emergency distribution of food and water cannot match needs, due to battered infrastructure and bureaucracy. There are also shortages of fuel outside gas stations.
Armed men were seen in the streets on Saturday attacking places where food and water were believed to be stored. Dominican media reported the shooting of two Dominican business people -- Carlos Gatas and Milton Matos -- as they were trying to hand out humanitarian aid they had brought from San Juan de la Maguana, into Haiti.
On of them suffered gunshot wounds to his back and the other was shot in the face and chest. They were both taken to a clinic in Dominican town Brahona.