US President Barack Obama says he has authorised air strikes against Islamic militants in northern Iraq but will not send US troops back to the country.

He said Islamic State (IS) fighters would be targeted to prevent the slaughter of religious minorities, or if they threaten US interests.

Strikes have not yet begun, but the US has made humanitarian air drops to Iraqis under threat from the militants.

IS has seized Qaraqosh, Iraq's biggest Christian town, forcing locals to flee.

The Sunni Muslim group, formerly known as Isis, has been gaining ground in northern Iraq and Syria for several months.
Islamic State militants stand guard after taking control of a government building in the Christian town of Bartella, Nineveh province - 7 August 2014 Islamic State fighters have taken control of large parts of northern Iraq since launching an offensive in June

In a rapid advance in June the group took control of the northern city of Mosul and advanced south towards Baghdad.

It now controls large swathes of Iraq and Syria and says it has created an Islamic caliphate in its territory.
'Coming to help'

Speaking at the White House, Mr Obama said US military aircraft had already dropped food and water to members of the Yazidi religious minority community trapped on Mount Sinjar by IS fighters.

The UN estimates that about 200,000 civilians have been displaced from the town of Sinjar and about 50,000 Yazidis are thought to have been trapped on the mountain.

The Yazidis face starvation and dehydration if they remain on the mountain, and slaughter at the hands of the IS if they flee, officials have warned.

Tens of thousands of Iraqi Christians and Yazidis are understood to have fled their homes in northern Iraq, as James Robbins reports

Mr Obama said the Iraqi government had requested assistance and the US would act "carefully and responsibly, to prevent a potential act of genocide".

US air strikes would target IS fighters if they threaten Baghdad or move towards the Kurdish capital of Irbil, where there is a significant presence of US diplomats and military advisers, Mr Obama said.

In addition, he authorised strikes "if necessary" to help Iraqi government forces break the siege at Mount Sinjar and rescue the trapped civilians.

"The only lasting solution is reconciliation among Iraqi communities and stronger Iraqi security forces," Mr Obama added.