UPDATE: US denies reports of bombings in Iraq after considering military intervention

The Pentagon has denied reports the US has bombed Iraq in the wake of increased aggression by the Islamic State militant group.

A spokesman for the Kurdish peshmerga force said US warplanes bombed jihadist targets in two areas of northern Iraq.

But the Pentagon Press Secretary has adamantly denied the bombings.

“Press reports that US has conducted airstrikes in Iraq completely false. No such action taken,” Rear Adm. John Kirby tweeted.

It comes after reports US president Barack Obama was considering US military action in Iraq.

Hundreds of thousands of Christians were forced to flee their homes, prompting the US to issue a warning that the jihadist offensive could provoke a "humanitarian catastrophe".

"It is a situation that that we are looking at very closely," White House spokesman Josh Earnest said, following reports that president Obama was talking with military advisors about options for intervention.

He would not confirm reports that US air strikes are on the table, but said American personnel were studying conditions on the ground in cooperation with Iraqi security forces.

"So if there are specific needs that need to be met in terms of enhancing Iraq security forces' capabilities, then we will look to provide it," he said.

"The United States strongly condemns ISIL's assault on Sinjar and surrounding areas of northern Iraq."

Louis Sako, the leader of Iraq's largest Christian denomination, described the situation as a "humanitarian disaster" and he feared it would result in a genocide.

"Today we appeal with lots of pain and sadness, to all people of good will, the UN Security Council, European Union and relief organisations, to help those people who are facing mortal danger," Mr Sako said.

"I hope it is not too late to avoid a genocide.”

Mr Earnest said the actions by the extremist group were exacerbated by the "dire humanitarian crisis" already facing Iraqi's.

"We're deeply concerned about reports that ISIL has abducted as many as several hundred girls from these vulnerable communities," he said.

"We're working intensively with the government of Iraq, the Iraqi security forces and the Kurdish authorities in the immediate area to support their efforts to address the humanitarian situation in Sinjar."

US media, citing senior White House officials, said president Obama was weighing military options for strikes against the jihadists and aid drops to the displaced and besieged civilians.

The UN Security Council has also called an emergency meeting on the crisis.