US agencies concerned over potential New Orleans copycat attacks

"The FBI and DHS are concerned about possible copycat or retaliatory attacks due to the persistent appeal of vehicle ramming as a tactic for aspiring violent extremist attackers," they said in a statement.

On New Year's Day, at least 14 people were killed and dozens injured in New Orleans when Shamsud-Din Jabbar, a US Army veteran, drove a pickup truck into a crowd of revelers in the French Quarter on Bourbon Street.

According to the FBI, Jabbar drove from Houston, Texas to New Orleans and posted several videos online expressing his support for ISIS (Daesh) shortly before the attack, which followed tactics encouraged by the terror group.

The agencies said attackers inspired by "foreign terrorist organizations" who have conducted vehicle attacks in the US and abroad have used rented, stolen and personally owned vehicles.

Some have used additional weapons such as firearms and knives to attack individuals after the vehicle has stopped, they said, adding attackers may attempt to conceal and pre-position improvised explosive devices to supplement a vehicle attack.

"Targets have included pedestrians, law enforcement or military members, and crowded public venues, including festivals and commercial centers, which generally are accessible from roadways.

"We ask that the public remain vigilant regarding possible copycat or retaliatory attacks and report any suspicious activity to law enforcement," the agencies said.