Traffic was closed and the United Nations headquarters in New York was cordoned off Thursday during a police standoff with a man allegedly holding a gun outside the venue, officials said.

"The U.N. headquarters is closed, there is police activity," a U.N. spokesperson told Agence France-Presse (AFP).

Images from the scene showed armed police surrounding the man standing on a sidewalk while holding what appeared to be a gun.

According to an official, speaking on condition of anonymity, the man threatened to kill himself in front of one of the building's entrances.

The avenue along the U.N. headquarters was closed to traffic, but meetings inside the building were not immediately interrupted.

"Due to a police investigation, avoid the area of 42 Street and 1st Avenue. Expect emergency vehicles in the surrounding area," the New York police department (NYPD) said on Twitter.

In October, the NYPD set up a police cordon and called in the bomb squad after a suspicious package was found near the U.N. building and newly opened Turkish House (Türkevi). The bomb squad was called to the scene and the area was cleared.