The heavily armed men, employed by private military companies including Blackwater and ISI, are part of the militarisation of a city which had a reputation for being one of the most relaxed and easy-going in America.

After scenes of looting and lawlessness in the days immediately after Hurricane Katrina struck, New Orleans has turned into an armed camp, patrolled by thousands of local, state and federal law enforcement officers, as well as 70,000 national guard troops and active-duty soldiers now based in the region.

Blackwater, one of the fastest-growing private security firms in the world, which achieved global prominence last year when four of its men were killed and their bodies mutilated in the Iraqi city of Falluja, has set up camp in the back garden of a vast mansion in the wealthy Uptown district of the city.

David Reagan, 52, a semi-retired US army colonel from Huntsville, Alabama, who fought in the first Gulf war and is commander of Blackwater's operations in the city, refused to say how many men he had in New Orleans but indicated it was in the hundreds.

Asked if they had encountered many looters so far, Mr Reagan said that the sight of his heavily armed men - a pump action shotgun was propped against the wall near to where he was standing - was enough to put most people off.

Two Israeli mercenaries from ISI, another private military company, were guarding Audubon Place, a gated community. Wearing bulletproof vests, they were carrying M16 assault rifles.

Gill, 40, and Yovi, 42, who refused to give their surnames, said they were army veterans of the Israeli war in Lebanon, but had been living in Houston for 17 years. They had been hired by Jimmy Reiss, a descendant of an old New Orleans family who made his fortune selling electronic systems to shipbuilders. They had been flown by private jet to Baton Rouge, the capital of Louisiana, and then helicoptered to Audubon Place, they said.

"I spoke to one of the other owners on the telephone earlier in the week," Yovi said. "I told him how the water had stopped just at the back gate. God watches out for the rich people, I guess."