"We have 71 trained soldiers in 15 different states ready at our word to attack any target we desire," the post on JustPasteIt website said Tuesday.
Virginia, Maryland, Illinois, California and Michigan are among the 15 states where IS has stationed its militants.
According to the message, out of these 71 trained soldiers, 23 signed up for attacks like the one carried out by IS on the Prophet Muhammad cartoon exhibition in Garland, Texas on Sunday.
The militant group also said in a post that its aim was the exhibition's organizer and controversial US blogger Pamela Geller.
"We will send all our Lions to achieve her slaughter," Islamic State said.
On Tuesday, IS said on its official radio that the attack on the cartoon exhibition was conducted by its fighters in protest of what it described as slander against the Prophet.
Islamic State has been mainly operating in Syria and Iraq, but it has been making attempts to branch out to other countries as well, Libya, Afghanistan and Pakistan among them.
