Authorities, however, say they are monitoring the site and there is no evidence of a threat from Al-Qaeda, which carried out the September 11, 2001 terrorist attacks that destroyed the World Trade Center and killed thousands of people.
The image shows a Manhattan skyline at sunset, with a man and his son walking down a sidewalk. To the left, the word "Al-Qaeda" stretches across the street in 3D letters, with "Coming soon again in New York" displayed beneath.
New York Police Department (NYPD) spokesperson Paul Browne said an overseas, Arabic-language Internet site posted the graphic on its "artwork and design" page, according to The Associated Press. He also said the NYPD has been monitoring the site.
FBI spokesperson J. Peter Donald said in a statement that while the agency takes all threats seriously, "there is no specific or credible threat to New York."
MSNBC News quoted Browne as saying that the website was categorized as "Category 1" by the NYPD Intelligence Division, meaning that it is highly trafficked by jihadi and Al-Qaeda adherents.
Reuters reported on April 2 that the graphic was posted on a militant web forum called the Ansar al Mujahiddin Arabic Forum, or AMAF, adding that the site allegedly has close connections to the Afghan Taliban and a key militant leader in Jordan.
Meanwhile, "The New York Daily News" reported that the graphic appeared on several Arabic-language websites, including gulfup.com, and quoted Browne as saying that cops believe the graphic was posted by an Egyptian who regularly uses the Internet to spread propaganda about Al-Qaeda.
The NYPD has come under fire in recent months for its antiterrorism campaign after an investigation by AP revealed that police subjected entire neighborhoods to surveillance and scrutiny, often because of the ethnicity of residents rather than any accusations of crimes. Student groups were investigated and dozens were infiltrated, in operations partly built with help from the CIA, which is prohibited from spying on Americans.
-- Courtney Brooks