Police in Haiti opened fire on Sunday on a group of looters in the capital Port-au-Prince, killing a man.
Hundreds of people ransacked the Hyppolite market in Port-au-Prince.
The ABC reports a man in his 30s, was shot in the head by police as the crowd took over.
Police reinforcements descended on the area armed with shotguns and assault rifles as the clashes went on.
The head of the US military contingent in Haiti says security is becoming an increasing concern.
Lieutenant General Ken Keen said it was feared that the death toll could be as high as 200,000.
However, he cautioned that "it's too early to tell exactly what the casualty count will be."
Port-au-Prince and other centres were devastated by a magnitude 7.0 earthquake on Tuesday.
Aid is now reaching desperate survivors, but the distribution is very slow because of congestion at the airport in Port-au-Prince. The port is blocked.