Food remains a problem for Haitians two weeks after the devastating quake as aid workers and local officials scramble to feed the hundreds of thousands of displaced people.

Improvement in aid material distribution was slow and food-related riots happened now and then, which officials feared might pose a threat to security in the aftermath of the 7.3-magnitude quake.

UN peacekeepers on Tuesday were forced to use tear gas to disperse desperate Haitians waiting for food handouts at the damaged presidential palace.

Food reaching the ravaged capital had been limited compared with the large number of people who had to rely solely on international help for survival, said the Brazilian peacekeepers.

A similar incident happened on Monday, when the Uruguayan troops had to form human walls to keep thousands of hungry Haitians in check before calling them one by one for rice and water distribution outside the presidential building.

The masses broke the cordon and stormed trucks loaded with relief materials. A man managed to dump the rice bags on the ground, and many were injured trying to grab them.

Haitian Health Minister Alex Larsen said 1 million Haitians had been displaced from their homes in the Port-au-Prince area. Authorities have launched a program to relocate the homeless to nearby suburb areas.

New villages will be built swiftly in the south and north of the Caribbean nation, with each having a capacity to house up to 10,000 people.

"It will take some time for the food infrastructure to come on line," World Food Programme (WFP) Executive Director Josette Sheeran said at a press conference at the UN Headquarters in New York on Monday.

Talking about the food riots, Sheeran said that "we are concerned that the most vulnerable -- children and women -- can easily get overrun."

Many countries and world groups pledged relief materials including tents, food and basic medical supplies after the catastrophe in Haiti.

But limited logistic capacities have hindered aid efforts: Some airplanes carrying aid supplies have to hover above its ravaged one-runway airport, more were kept on hold in the donating countries.

Italy recently criticized the inefficient coordination in Haiti. What lacked was a real leadership on the ground, said the Italian government special envoy to Haiti, Civil Protection Chief Guido Bertolaso.

Bertolaso, who successfully led the relief effort following the April earthquake in Italy's central region of Abruzzo, criticized the absence of central coordination in the international aid machine largely directed by the United States.

It sent too many troops and not enough people trained in disaster management, said Bertolaso.

Meanwhile, the Haitian government and the United Nations are working closely together to capture thousands of inmates who had escaped from Haiti's jails after the Jan. 12 quake.

More than 5,000 prisoners are at large, according to the United Nations Stabilization Mission in Haiti (Minustah).

Minustah spokesman Vicenzo Pugliese denied links between the inmates and sporadic violence in Port-au-Prince. He said there was no evidence to back up stories that prisoners had raided arsenals or that they were behind violent raids on stores.

Pugliese said that the United Nations had 990 policemen on the ground and 1,110 anti-riot officers on their way to the battered Caribbean nation.