Staffers noticed the false tweets at around 6 p.m. Eastern time Friday, contacted Twitter and soon after had the account suspended.
Host Brian Williams then read a statement on air saying the reports were false.
A group calling themselves Script Kiddies mentioned themselves in the tweets and appeared to be responsible.
By about 7 p.m. Eastern, the account was restored and the false tweets removed. NBC is contacting authorities including the New York Police Department and FBI about the incident.
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