Tens of thousands of civilians remain trapped by militants on a mountain in northern Iraq and need "life-saving assistance", the United Nations warns.

Members of the Yazidi sect fled there 10 days ago after fighters from Islamic State (IS) seized the town of Sinjar.

US air strikes continued on Tuesday, with a drone targeting an IS mortar near Kurdish troops, the Pentagon said.

On Monday, Iraq's president asked MP Haider al-Abadi to form a new cabinet, snubbing the incumbent PM Nouri Maliki.

Mr Abadi's appointment came after months of political infighting, which analysts say is partially to blame for Iraq's inability to effectively fight the IS threat.

Politicians had been unable to form a government since April's parliamentary elections, which were won by Prime Minister Maliki.

IS fighters have seized large swathes of northern Iraq and Syria in recent months, forcing tens of thousands of people from religious minorities to flee their homes.
'A genocide'

UN Secretary-General Ban Ki-Moon urged countries to do more to help Iraqi civilians.

"The plight of Yazidis and others on Mount Sinjar is especially harrowing," he said.

An estimated 20,000 to 30,000 people remain trapped on Mount Sinjar without food, water or shelter said the UN's Adrian Edwards in a statement.

There are now an estimated 1.2 million internally displaced Iraqis, he added.

Keiran Dwyer, who works for the UN's office for humanitarian affairs in Irbil, told the BBC that some Yazidis had managed to escape from the north side of the mountain in the last 72 hours and cross the River Tigris into Syria, where they were receiving help.

But a Yazidi relief worker, who was on board an Iraqi Air Force helicopter evacuating the trapped refugees, described the situation as "a genocide" and said that he had seen what looked like "hundreds" of dead bodies on the ground.

"You can imagine what it's like when you land amongst 5,000 people and can only take 10 or 20, and everybody tries to get on the helicopter," Mirza Dinnay told the BBC.

BBC