Washington (AFP) - More than 1,800 US newspapers have closed since 2004, leaving expanding "news deserts" with little or no local reporting on public affairs, researchers said in a report Monday.

The study by the University of North Carolina School of Media and Journalism, an update of a 2016 paper, found that more than one-fifth of local dailies or weeklies had been shuttered in a decade and a half.

As a result, "thousands of our communities (are) at risk of becoming news deserts," the report said.

Half of the 3,143 counties in the United States now have only one newspaper, usually a small weekly, and almost 200 counties in the country have no newspaper at all.

"The people with the least access to local news are often the most vulnerable -- the poorest, least educated and most isolated," the report said.

The report was the latest to highlight the grim state of the once-thriving newspaper industry. A separate Pew Research Center report this year showed newsroom jobs fell 23 percent since 2008, mostly in newspapers.

The UNC researchers said the loss of so many local newspapers -- resulting from the digital disruption of the industry -- makes it more difficult to keep citizens informed and hold public officials accountable.

While the US still has some 7,100 surviving newspapers, many are "ghosts" of their former selves with reduced staff and far less newsroom resources.

Despite an abundance of national and global news online, coverage is diminishing of key local issues such as taxes, zoning and education, the report noted.

Some efforts are being made to fill the gap by television journalists or digital sites, according to the report, but most of these are clustered around major metropolitan areas.

"There are no easy fixes," the report said.

"We need to make sure that whatever replaces the 20th century version of local newspapers serves the same community-building functions."

As part of the upheaval, more than half of all newspapers have changed ownership in the past decade, and the largest 25 chains own a third of all newspapers.

"Not surprisingly, the number of independent owners has declined significantly in recent years, as family-owned papers have thrown in the towel and sold to the big guys," said the researchers led by professor Penelope Abernathy.

"The consolidation in the industry places decisions about the future of individual papers, as well as the communities where they are located, into the hands of owners with no direct stake in the outcome."