More details of "credible" terror threat emerged Thursday night of individuals trying to carry out attacks on the United States using truck or car bombs, while President Barack Obama has ordered increased security.

The new World Trade Center building under construction is seen in New York, the United States, Sept. 5, 2011. (Xinhua/Fan Xia)
ABC news, quoting intelligence officials, reported at least three individuals -- one believed to be a U.S. citizen -- entered the country in August in an attempt to launch a "vehicle-borne attack against Washington D.C. or New York around the anniversary of 9/11."

The suspected terrorists were believed to be coming from Afghanistan, and traveled through at least one other country, the report said.

It also said U.S. law enforcement agencies are seeking at least two rental trucks nationwide. Those trucks were missing from locations in Kansas City, Missouri. It was not immediately known whether the search was connected to the plot.

White House officials said President Obama was briefed on the matter, and he had ordered federal agencies to boost security.

Word of the threat came earlier in the evening, and authorities were investigating a "specific, credible threat" -- the first received in relation to the 9/11 anniversary.

VietNamNet/Xinhuanet