A man set himself on fire Friday outside the courthouse in Manhattan where former President Donald Trump's hush-money trial is being held.

After dousing himself in a liquid, he threw pamphlets in the air in front of news media gathered nearby.

The man's motive is unknown and police responded to the scene.

Mr Trump was inside the building to attend jury selection, where he has had a security detail, but the former president left during the incident.

Emergency officials said that court security had not been breached in the incident. The case, which had just completed alternate jury selection, resumed later in the afternoon. Opening statements are expected to begin Monday.

In a news conference, investigators said they received a 911 emergency call around 13:30 local time (18:30 BMT) telling them that a man had lit himself on fire.

They identified him as Maxwell Azzarello, who had arrived in New York from his home in Florida sometime in the past week. He has no criminal record in New York, and his family in Florida was unaware that he had travelled to the city.

New York Police Chief Jeffrey Maddrey said Azzarello was seen "shuffling around" in the park before reaching into a bag for the flammable liquid and pamphlets.

The pamphlets were "propaganda-based" said Chief Maddrey, adding that they were regarding a "conspiracy theory". The fuel appears to an alcohol-based cleaning product.

There was a massive police presence outside the courthouse due to the trial, and officers quickly ran into the park shouting for a fire extinguisher.

Azzarello was carried away on a stretcher, his body very badly burned. The police said he was taken to a hospital burn centre in critical condition.

Witness Julie Berman told reporters "It was hot, and it didn't make a lot sense. The whole thing happened so fast... it took me like 20 seconds to figure out what was going on.''

Another witness told BBC News that the scene was something "I never wanted to see.''

NYPD investigators later were seen collecting pamphlets that Azzarello had scattered before self-immolating. They have deemed the area safe.

Investigators are still interviewing witnesses and said he didn't appear to say anything before setting fire to himself.

Three NYPD officers and one court officer had minor injuries after helping to extinguish the blaze.

Officials said they will now reassess security outside the court. (BBC)