The US homeless population increased by more than 18% in a year, driven by high housing costs, natural disasters and a spike in migration to large cities, government officials said.

The Department of Housing and Urban Development (Hud) said Friday that more than 770,000 people were in shelters, temporary housing or had no shelter, according to a survey carried out one night in January 2024.

The number follows a 12% increase the previous year and is the highest since the federal government began an annual count of the homeless population in 2007.

The figure is likely an undercount, as it does not include people temporarily staying with family and friends.

Authorities cautioned that the data is nearly a year old and that both rents and the situation at the US border have changed since the survey was carried out.

Family homelessness overall rose 39% from the year before, and more than doubled in 13 places that said they had been affected by migration.

That was in contrast to the more than 370 other local areas that did not report being affected by migration, where family homelessness rose less than 8% on average.

Children under 18 experienced the biggest increase, with nearly 150,000 homeless on the night of the survey. There was a 6% increase in the homeless population aged 65 or older.

There were also some positive trends noted in the report. Homelessness among military veterans fell 8%, continuing a years-long decline, and some cities were able to get homeless residents off the streets.

Los Angeles, which has some of the highest housing costs in the country, saw its homeless population shrink by 5%, the first decline in seven years, Hud officials said.

The number of homeless people in Dallas fell 16% over two years, and Chester County, near Philadelphia in Pennsylvania, registered a 60% decrease over five years due to legal and education programmes, increasing affordable housing and homelessness prevention efforts aimed at migrant workers, officials said.

Some local authorities said an increasing number of asylum seekers resulted in higher figures.

In recent years record numbers have attempted to enter the US, and starting in late 2022 Republican governors in Texas and Florida sent tens of thousands of migrants to Democrat-controlled cities such as New York, Chicago and Denver, where many were housed in temporary shelters.

The report noted that unlawful crossings at the US border have dropped more than 60% since January's homelessness tally, and encounters at the border itself are at their lowest level since July 2020. Authorities in several major cities have begun closing migrant shelters.

The report also noted that the survey was taken after a period of rent spikes, and that rents "are flat or even down in many cities since January."

Natural disasters were another factor driving the high numbers.

The count included more than 5,200 people who were sleeping in emergency shelters in Hawaii, after devastating wildfires in Maui in August 2023.