The United Nations is concerned at the rise in looting and attacks targeting emergency aid deliveries in hurricane-ravaged Haiti, a UN official told AFP on Sunday.

Food, medicine and other essential aid has been slow to reach many hard-hit areas. Some desperate Haitians have taken to blocking parts of the road crossing the southern peninsula to intercept humanitarian convoys, in some cases looting them.

"It's obviously a concern for the coordination and delivery of aid," said Mourad Wahba, the UN humanitarian coordinator in Haiti. "But the response must focus on more than security."

"People are hungry and we must successfully unblock the roads to help them."

On Saturday, a World Food Program truck with relief supplies was looted at the entrance to the UN base in the port city Les Cayes, one of the worst affected by Hurricane Matthew which crashed ashore on October 4 with winds of 145 miles (230 kilometers) per hour.

In one violent scene -- which occurred shortly before UN Secretary General Ban Ki-moon arrived at the base via helicopter -- Senegalese UN peacekeepers used tear gas to disperse the crowd, which responded by throwing rocks, Wahba said.

"Any attack on a humanitarian convoy is an attack on those who are suffering, on those who are most in need," said Ban on his return to Port-au-Prince.

"When trucks with medicine are attacked and looted, when food and water are looted, this only increases the distress and discourages international aid," he said.

The UN estimates at least 1.4 million people of the impoverished nation's more than 10 million residents need urgent assistance, after towns and villages were almost wiped off the map.

At least 546 people were killed, and more than 175,000 people have lost their homes.

The international body has launched a flash appeal for $120 million to help Haiti -- the poorest country in the Western Hemisphere -- cope with its worst humanitarian crisis since a devastating 2010 earthquake.

So far, only about 13 percent of the needed funds has been raised to help stave off famine and serious health crises, including cholera.