Two months of violence have brought Iraq to the brink of breakup, and world powers relieved by the exit of long-time premier Nuri al-Maliki were flying aid to the displaced and arms to the Kurds.
Kurdish forces attacked the IS fighters who wrested the Mosul dam from them a week earlier, a general told AFP.
"Kurdish peshmerga, with US air support, have seized control of the eastern side of the dam" complex, Major General Abdelrahman Korini told AFP, saying several jihadists had been killed.
The dam on the Tigris provides electricity to much of the region and is crucial to irrigation in vast farming areas in Nineveh province.
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The recapture of Mosul dam would be one of the most significant achievements in a fightback that is also getting international material support.
A day after the European Union foreign ministers encouraged the bloc's member countries to send arms to the Kurds, German Foreign Minister Frank-Walter Steinmeier visited Iraq.
Fear of an impending genocide against the Yazidi minority, whose faith is anathema to the Sunni Muslim extremists, was one reason Washington cited for air strikes it began on August 8.
Obama declared the Mount Sinjar siege over on Thursday, but vulnerable civilians remain in areas taken by the jihadists.
In Kocho, senior Kurdish official Hoshyar Zebari said the jihadists "took their revenge on its inhabitants, who happened to be mostly Yazidis who did not flee their homes".
A senior official of one of Iraq's main Kurdish parties said 81 people had lost their lives in the attack yesterday, while a Yazidi activist said the death toll could be even higher.
The village lies near the northwestern town of Sinjar, which the jihadists stormed on August 3 sending tens of thousands of civilians, many of them Yazidi Kurds, fleeing into the mountains to the north.