Yazidi refugees in Iraq 'facing genocide' receive second US airdrop of aid

Pallets of bottled water are loaded on board a C17 transport plane for an airdrop to Iraqi refugees. Photograph: Sgt Vernon Young/US Air Force/EPA

The US has carried out a second airdrop of food and water to thousands of displaced Iraqis hiding in mountains amid the fear of genocide by Islamist militants, the Pentagon has said.

The operation to aid 40,000 civilians, Kurds mostly of the Yazidi faith, who are besieged on Mount Sinjar, on the western edge of Kurdistan's border with the rest of Iraq, came hours after the US launched fresh air strikes against fighters from the Islamic State in Iraq and the Levant (Isis). The raids have pulled the US back into Iraqi conflict for the first time since Barack Obama withdrew ground troops in 2011.

The chief spokesman for the Pentagon, Rear Admiral John Kirby, said early on Saturday that the air strikes had been followed up by further relief drops. Three planes delivered 72 bundles of supplies for the refugees, including more than 28,000 meals and more than 6,800 litres of water.

Yazidi children who fled the violence in Nineveh are taken to the relative safety of Sulaimaniya province in Kurdistan. Photograph: Reuters

The first aid consignment from Britain has left RAF Brize Norton to be dropped from C130 aircraft over the weekend.

Downing Street has ruled out military action at this stage in favour of delivering humanitarian aid. The UK's £8m emergency package includes drinking water, reusable filtration containers, tents and solar lights that can also recharge mobile phones.

David Cameron said it was the world's duty to help religious minorities "in their hour of desperate need".

It has been reported that children among the stranded population, who face slaughter by the encircling jihadists, were beginning to die of thirst on the bare, parched mountainside. Isis has captured hundreds of women from the Yazidi religious minority, according to an Iraqi official, while thousands of other civilians fled in fear.

The US secretary of state, John Kerry, said the extremists' "campaign of terror against the innocent, including the Yazidi and Christian minorities, and its grotesque and targeted acts of violence bear all the warning signs and hallmarks of genocide. For anyone who needed a wake-up call, this is it."

The US is putting pressuring on Iraqi leaders to form a unity government capable of dealing with Isis, which has recently captured further territory in northern Iraq and is threatening the Kurdish capital of Irbil.

US warplanes bombed Isis fighters outside Irbil on Friday, launching a second and third round later in the day. The first strikes were limited to the frontlines around the city to relieve intense pressure on US-backed Kurdish fighters, but the White House signalled it could expand its military commitment.

However, the Obama administration stressed that sending US combat troops back into the country was not an option.

The first 225kg laser-guided bombs were dropped in mid-afternoon by two fighter jets flying from an aircraft carrier in the Gulf. They targeted a howitzer that Isis fighters were using to shell Kurdish forces, known as peshmerga.

A second and third wave of bombing resumed in the evening, with attacks on Isis lines outside Irbil, the largest city in the autonomous Kurdistan region, with a population of 1.5 million inflated by thousands of Arab refugees from fighting elsewhere in Iraq. A drone hit an Isis mortar position near the city and a second pass by the drone killed suspected Isis militants when they "returned to the site moments later"