UNITED NATIONS: The United Nations headquarters in New York was cordoned off on Thursday during a police stand-off with a lone man apparently holding a gun outside the venue, officials said.

"The UN headquarters is closed, there is police activity," a UN spokesman told AFP.

Images 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 UN headquarters was closed to traffic, but meetings inside were not immediately affected.

"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 said on Twitter.

This is a developing story, and will be updated accordingly