A video released today by the Islamic State (IS) urges Muslims to "slaughter" Westerners from those nations which are taking part in an international anti-jihadist coalition.
In a disturbing 42-minute address, spokesman for the terrorist group, Abu Mohammed al-Adnani, says: "If you can kill a disbelieving American or European, especially the spiteful and filthy French, or an Australian, or a Canadian ... including the citizens of the countries that entered into a coalition against Islamic State, then rely upon Allah, and kill him.
"Smash his head with a rock, or slaughter him with a knife, or run him over with your car, or throw him down from a high place, or choke him, or poison him."
Adnani says both civilians and members of the military are "disbelievers" and therefore "both of their blood and wealth is legal for you to destroy".
Also targeting President Obama, who is leading the fight against IS, Adnani mocks the administration's ruling that America will not enter into a war on the ground in Iraq and Syria.
"No, it will be drawn and dragged. It will come down to the ground and it will be led to its death, grave, and destruction" Adnani says, referring to the president as "the mule of the Jews" and ridiculing the suggestion that the Islamic State is not truly Muslim.
Adnani continues his threat against Westerners, saying : "You will not feel secure even in your bedrooms. You will pay the price when this crusade of yours collapses, and thereafter we will strike you in your homeland, and you will never be able to harm anyone afterwards.
"O America, O allies of America, and O crusaders, know that the matter is more dangerous than you have imagined and greater than you have envisioned," he adds.
"We have warned you that today we are in a new era, an era where the [Islamic] State, its soldiers, and its sons are leaders, not slaves.
"We will conquer your Rome, break your crosses, and enslave your women, by the permission of Allah, the Exalted."
The video follows French airstrikes against IS on Friday, which killed dozens of jihadist fighters in northern Iraq.
Other countries have also stepped up their responses to the militant group, with further air strikes expected from the US this week.
According to US Secretary of State John Kerry, more than 50 countries have pledged to join an international coalition against IS, which is thought to have between 20,000 and 31,500 members fighting to create an Islamic caliphate. The group now controls a large stretch of Iraq and Syria.
As part of the effort to eliminate the extremists, President Obama will this week urge the UN to pass a resolution banning would-be jihadists from travelling overseas.