Donald Trump on Tuesday compared his own legal troubles with the persecution of Russian opposition figure Alexei Navalny, who died in prison last week.

The former US president and current frontrunner for the 2024 nomination again refused to criticize Russian leader Vladimir Putin over Navalny's unexplained death, despite being offered the chance during a town hall meeting in South Carolina.

Navalny died suddenly at age 47 in an Arctic prison, shocking Russia's exiled opposition as well as the West, where leaders, including US President Joe Biden, have blamed the Kremlin.

In the hour-long appearance broadcast on Fox News, Trump railed against the $355 million fine meted out to him in a New York fraud trial, saying "it's a form of Navalny."

"It is a form of communism or fascism," he added.

Despite prodding from host Laura Ingraham, Trump did not mention Putin when asked about Navalny, though he lamented "a very sad situation."

"He was a very brave guy because he went back. He could have stayed away, and frankly, probably would have been a lot better off staying away and talking from outside of the country."

But, Trump added: "It's happening in our country, too. We are turning into a communist country in many ways.

"I have eight or nine trials all because of the fact that... I'm in politics," he said

"If I were losing in the polls, they wouldn't even be talking about me and I wouldn't have had any legal fees," he alleged.

In addition to the civil fraud case in New York, Trump faces 91 criminal counts, including charges related to alleged electoral interference in the 2020 election, which he lost to Joe Biden.

He has seized on his legal woes as a way to fire up supporters, claiming court cases are "just a way of hurting me in the election."

Trump has long soft-pedaled on Russia, at times expressing open admiration for Putin, whom he has called a "genius."

Earlier this month he effectively killed a bipartisan bill that would have sent billions of dollars in military aid to Ukraine after telling congressional Republicans to vote the legislation down.

He also recently stunned Western allies after saying he would "encourage" Russia to attack members of the NATO military alliance who had not met their financial obligations.