A man set himself on fire Friday outside the court where Donald Trump is standing trial in Manhattan, with officers rushing to extinguish the flames.

Burning clothes were strewn in the park, which was locked down by authorities, while ambulances lined up nearby on standby, an AFP correspondent at the scene saw, describing a strong smell of burning chemicals.

TV reporters described the scene that unfolded moments after the full panel of 12 jurors and six alternates was selected for the trial of the former president in a hush money cover-up case.

"A male did light himself on fire outside of the Supreme Courthouse. We're still gathering details from the field," said a New York Police Department spokesman.

The fire department did not respond to a request for comment, but media reported the man had been taken away for medical treatment.

The incident happened in a park opposite the 100 Centre Street courthouse, which has been used by authorities to corral protesters, both pro-Trump and anti-Trump, as well as well as by some members of the media.

The park, which is close to several courthouses and other buildings, is a popular local lunch spot.

Trump's criminal trial, the first of a former president, is being conducted amid tight security in a 15th-floor courtroom swarming with Secret Service officers as well as court police.

New York's police department had promised a major deployment to ensure the trial passes off safely, with the force's head of intelligence John Hart calling it a "major challenge."