Former New York City mayor Rudy Giuliani has been injured in a car accident in the US state of New Hampshire, his security guard has said.

Giuliani's car was struck from behind at high speed while travelling on a highway, according to a statement posted on social media.

"He was diagnosed with a fractured thoracic vertebrae, multiple lacerations and contusions, as well as injuries to his left arm and lower leg," the statement from security guard Michael Ragusa says.

Giuliani, 81, became known as "America's Mayor" after leading New York through 9/11. He later became an adviser and then personal lawyer to Donald Trump, though the two have since parted ways.

Giuliani was taken to a nearby hospital for treatment, Mr Ragusa said.

The incident happened shortly after Giuliani had helped an alleged victim of domestic violence who had flagged him down on a road, his statement added.

"Mayor Giuliani immediately rendered assistance and contacted 911."

The BBC has approached local police for comment.

The thoracic vertebrae form the middle section of the spine, while lacerations and contusions are deep cuts and bruises, respectively.

First elected New York City mayor in 1993, Giuliani was in charge at the time of the 11 September attack on the World Trade Centre in 2001.

In 2008, he made an unsuccessful run for US president, and later became one of Trump's advisers during the latter's 2016 campaign. He joined Trump's personal legal team in 2018 and remained a part of it through to the 2020 election.

In the aftermath of Joe Biden's 2020 election victory over Trump, Giuliani spread baseless claims that the election was stolen.

Earlier this year, he reached a tentative settlement with two former election workers who won $148m (£120m) in damages after they successfully sued him for defamation over false election fraud claims.