An estimated 90% of the capital Port-au-Prince is now under control of criminal groups who are expanding attacks into previously peaceful areas, a U.N. official said.

Haiti's gangs have gained "near-total control" of the capital and authorities are unable to stop escalating violence across the impoverished Caribbean nation, senior UN officials warned Wednesday.

Violent armed gangs now have some 90 per cent of Port-au-Prince under their grip, said Ghada Waly, director of the UN Office on Drugs and Crime. The previous assessment was 85 per cent.