A judge in the US has ruled that the effective closure of the Voice of America (VOA) last year was "illegal" and that hundreds of its journalists should be reinstated.

District Court Judge Royce Lamberth has given authorities one week to put the international broadcaster back on air.

The VOA was set up during World War Two to counter Nazi propaganda.

Just weeks after returning to office as president, Donald Trump issued an executive order to close the broadcaster, which his officials accused of left-wing bias. Trump also ordered outlets such as Radio Free Europe and Radio Free Asia to be "eliminated to the maximum extent consistent with applicable law."

The president appointed Kari Lake to head the US Agency for Global Media (USAGM), the parent company that oversees and funds the VOA as well as Radio Free Europe and Radio Free Asia.

Lake proceeded to sack more than 85% of the agency's employees, more than 1,000 staff at VOA alone, leaving just a handful of employees in their jobs.

Most have been on paid administrative leave since last year, including Persian Service reporters who were called back to work after Israel attacked Iran last June.

Last week, Judge Lamberth ruled that Lake did not have authority to order the suspension of the USAGM workforce as she had not been confirmed by the US Senate.

In Tuesday's ruling, the federal judge described the decision to sack the journalists as "arbitrary and capricious," adding that the government had not taken into account legislation that determines what languages and regions the VOA must serve.

"Defendants have provided nothing approaching a principled basis for their decision," Lamberth wrote.

Three VOA journalists had sued the Trump administration. One of them, Patsy Widakuswara, said she was deeply grateful for the judge's decision.

"We hope the American people will continue to support our mission to produce journalism, not propaganda," she told the Associated Press news agency.

It is not clear if Lake's nominated successor, Sarah Rogers, whose appointment needs Senate confirmation, will appeal.

Before being wound down, the VOA broadcast TV, radio, and digital content in almost 50 languages.

Trump's criticisms of the VOA form part of his broader attacks against the US media, which studies suggest American news consumers view as highly polarised.