Rudy Giuliani, the former New York City Mayor and a long-time champion of President Donald Trump, is in a "stable but critical condition" in hospital, his spokesman Ted Goodman said in a social media post on Sunday.

Shortly after Goodman's post was published, Trump wrote on social media: "Our fabulous Rudy Giuliani, a True Warrior, and the Best Mayor in the History of New York City, BY FAR, has been hospitalised, and is in critical condition."

He went on to praise Giuliani's efforts contesting the 2020 election results on his behalf, adding, "he was treated so badly by the Radical Left Lunatics".

Goodman did not give further details. Giuliani was injured in a car accident late last year.

Giuliani became known as "America's Mayor" after leading New York City through the aftermath of the 9/11 attacks.

After the 2020 presidential election, Giuliani and other advisers travelled across the country, accusing Trump's opponent, former President Joe Biden, of attempting to steal the election and making false claims about the results.

Later, a jury forced him to pay two election workers whom he had accused of ballot fraud $148m (£108m) for defamation.

"Mayor Giuliani is a fighter who has faced every challenge in his life with unwavering strength, and he's fighting with that same level of strength as we speak," Goodman said in the social media post.

He added, "We do ask that you join us in prayer for America's Mayor Rudy Giuliani."

Last September, Giuliani, who will turn 82 this month, was a passenger in a Ford Bronco when it was struck from behind in the US state of New Hampshire.

He suffered a fractured thoracic vertebra, multiple lacerations and contusions, and injuries to his left arm and lower leg, his security guard said at the time.