Iraq crisis: US strikes aid Kurdish bid to retake dam
Kurdish Peshmerga fighters have shelled militants' positions, and there is an unconfirmed report of a ground attack.
At least 11 IS fighters have been killed, sources in Mosul told BBC News.
The extreme Sunni group, which overran Mosul this summer, has been accused of a new massacre of non-Muslims.
At least 80 men from the Yazidi faith were killed, and scores of women and children abducted, in the village of Kawju (also spelt Kocho) on Friday.
Reports say the men were killed after refusing to convert to Islam. A US drone strike later destroyed two vehicles belonging to the militants.
In another development, German Foreign Minister Frank-Walter Steinmeier visited Iraq, as Western states stepped up aid.
'Heaviest yet' Reports on Saturday morning said US aircraft had launched strikes on IS positions near the strategic dam in Mosul.
US military officials told NBC News the decision to try to retake the dam came after intelligence showed IS militants "were not yet at a point where they could blow up the installation".
A Kurdish commander, Major General Abdelrahman Korini, told AFP that the Peshmerga had captured the eastern side of the dam and were "still advancing".
Rudaw, a Kurdish news website, said the air strikes appeared to be the "heaviest US bombing of militant positions since the start of air strikes" against IS last week.
The dam, captured by IS on 7 August, is of huge strategic significance in terms of water and power resources.
Located on the River Tigris about 50km (30 miles) upstream from the city of Mosul, it controls the water and power supply to a large surrounding area in northern Iraq.
The BBC's Jim Muir in Irbil says there are fears the dam is structurally dubious and many have warned that it could unleash a catastrophic flood if it was breached.
New leadership Visiting Baghdad, Germany's foreign minister met the new Prime Minister, Haider al-Abadi, who took over from Nouri Maliki this week.
He said he hoped Mr Abadi would be able to represent all the different regions and religions in the country, as this was the only way to prevent disenchanted Iraqis from backing IS.
Two Airbus flights carrying UK aid supplies arrived in Irbil on Saturday.
On a stop in the city, Mr Steinmeier met Yazidi refugees.
IS-led violence has driven an estimated 1.2 million Iraqis from their homes. Whole communities of Yazidis and Christians have been forced to flee in the north, along with Shia Iraqis, who IS do not regard as true Muslims.