Iraq crisis: US launches first air strike against militants as Kerry warns Isis campaign shows 'all the signs of genocide'

John Kerry has declared a campaign by Islamic militants to overrun Iraq has “all the warning signs of genocide” as the US launched its first air strike against Islamic State artillery.

The Pentagon said American aircraft launched an attack on artillery used by militants against Kurdish forces defending the city of Irbil.

Two F/A-18 aircraft dropped 500-pound laser-guided bombs on a mobile artillery piece, Pentagon press secretary Rear Admiral John Kirby said in a statement.

He said the Islamic rebels had been using the artillery to shell Kurdish forces near where US personnel are located.

The move came just hours after Mr Obama authorised limited air strikes in Iraq to slow the rapid advance of Isis fighters, who have seized parts of the country.

Earlier Mr Kerry was quoted by Sky News as telling a conference in Afghanistan: “The stakes for Iraq's future can also not be more clear.

"Isis's campaign of terror against the innocent, including the Christian minority, and its grotesque targeted acts of violence show all the warning signs of genocide.”

In a late night statement, Mr Obama also confirmed US planes have delivered essential supplies to 40,000 Iraqis of the minority Yazidi religion who have fled into a mountainous area in north Iraq for fear of being slaughtered by the ISIS forces.

Many are trapped on Mount Sinjar without food or water by fighters surrounding the mountain.

Militants have also captured Mosul, Iraq’s second biggest city, where Christians have been fleeing after an ultimatum was issued demanding they pay a special tax, convert, or face death.

During the conference, Mr Obama was quick to stress strikes did not mean troops back on the ground, saying: “As commander in chief, I will not allow the United States to be drawn into fighting another war in Iraq.”

Meanwhile, David Cameron condemned attacks carried out by Isis as “barbaric”, but stressed he would not be ordering any military intervention in Iraq.

Mr Cameron said he "fully agreed" with the President's view "that we should stand up for the values we believe in", and remains “especially concerned” for the Yazidi community.

"I have tasked officials to urgently establish what more we can do to provide help to those affected, including those in grave need of food, water and shelter in the Sinjar area," he said.

"They fear slaughter if they descend back down the slopes but face starvation and dehydration if they remain on the mountain. The world must help them in their hour of desperate need."

The French President François Hollande also spoke on Friday, saying France was ready to take part in action to end civilian suffering in Iraq. "We are ready to take responsibility for our part," Mr Hollande said in a statement.