There was an incident in New York City involving a lone gunman and police that caused massive delays and traffic as police dealt with the situation.

Police cordoned off the United Nations headquarters in New York City in the United States of America on Thursday.

The New York Police Department (NYPD) cordoned off the area following a standoff between them and a lone gunman who was on a suicide mission.

Videos and Images that circulated across social media showed the lone gunman carrying what appeared to be a shotgun pacing up and down the sidewalk.

The street that is in front of the UN, 1st Avenue in Manhattan and the adjacent one, 42 Street, were closed off to the public due to police activity.

NYPD cautioned the public through its official Twitter handle to avoid the area and use alternative routes as they expected emergency vehicles in the surrounding area.

“ADVISORY: Due to a police investigation, avoid the area of 42 Street and 1st Avenue. Expect emergency vehicles in the surrounding area. Traffic along the FDR Drive is affected. Use an alternate route if travelling in the area,” NYPD Twitted.

They engaged the gunman in a negotiation, trying to convince him to drop his weapon and surrender.

The Caucasian man, who is believed to be in his sixties, reportedly threatened to take his own life in front of the building’s entrances.

However, meetings in the building proceeded unaffected and no injuries were reported.

NYPD confirmed the man was in custody after a three-hour standoff and is no longer a threat to the public.

"In regard to reports of a man with a firearm at 42nd Street and 1st Avenue in Manhattan—the individual is now in custody and there is NO THREAT to the public," NYPD said.