Encampments and shanty towns are increasing across the US with more people losing jobs and shelters on the back of a deepening recession.

"They just popped up about 18 months ago," said homeless advocate Paul Stack, according to a New York Times article released on Thursday. "One day it was empty. The next day, there were people living there."

While Americans residing in big cities like Los Angeles and New York are already familiar with tent cities, the number of homeless is spreading like wildfire across the US.

"These are able-bodied folks that did day labor, at minimum wage or better, who were previously able to house themselves based on their income," said Michael Stoops, the executive director of the National Coalition for the Homeless -- an advocacy group based in Washington.

In Fresno, California's fifth largest city of 500,000 people, there are now an estimated 2,000 people without shelter, according to Gregory Barfield, the city's homeless prevention and policy manager.

Barfield claims that drug use, prostitution and violence are quite common in tent cities.

"That's all part of that underground economy," he said. "It's what happens when a person is trying to survive."

Asked recently about growing shanty towns, President Barack Obama said that it was "not acceptable for children and families to be without a roof over their heads in a country as wealthy as ours."

RB/AA