Airstrikes meanwhile targeted insurgents around Iraq's largest dam, which was captured by the Islamic State extremist group earlier this month, according to nearby residents. It was not immediately clear who carried out the strikes.
The U.S. began launching airstrikes against the Islamic State extremist group a week ago, in part to prevent the massacre of tens of thousands of Yazidis stranded on a northern mountaintop. After most were able to escape with the help of Kurdish fighters, President Barack Obama took credit for alleviating the threat of genocide.
But on Friday afternoon Islamic State fighters who had surrounded the nearby village of Kocho 12 days ago, demanding its Yazidi residents convert or die, moved in.
The militants took the men away in groups of a few dozen and shot them dead with assault rifles on the edge of the village, according to a wounded man who escaped by feigning death.
The fighters then walked among the bodies, finishing off any who appeared to still be alive with their pistols, the 42-year-old man told the Associated Press by phone from an area where he was hiding out. He spoke on condition of anonymity, fearing for his safety.
"They thought we were dead, and when they went away, we ran away. We hid in a valley until sundown, and then we fled to the mountains," he said.
A Yazidi lawmaker, a Kurdish security official and an Iraqi official from the nearby city of Sinjar gave similar accounts, saying Islamic State fighters had massacred scores of Yazidi men Friday afternoon after seizing Kocho.
All said they based their information on the accounts of survivors and warned that the minority group remains in danger despite the U.S. intervention. Their accounts matched those of two other Yazidi men, Qassim Hussein and Nayef Jassem, who said they spoke to other survivors.
The Yazidis are a centuries-old religious minority viewed as apostates by the extremist Islamic State group, which has claimed mass killings of its opponents in Syria and Iraq, often posting grisly photos on the Internet.
Yazidi lawmaker Mahma Khalil said the Yazidis in Kocho were given the choice to convert or die. "When the residents refused to do this, the massacre took place," he said.
Halgurd Hekmat, a spokesman for Kurdish security forces, said the militants took the women and children of Kocho to the nearby city of Tal Afar, which is controlled by the Islamic State group.
Elsewhere in northern Iraq, residents living near the Mosul Dam told The Associated Press that the area was being targeted by airstrikes, but it was not immediately clear whether the attacks were being carried out by Iraq's air force or the United States.
A Pentagon spokeswoman said the Defense Department, for the safety and security of American personnel, would not discuss reports of ongoing or future operations. Iraqi military spokesmen could not immediately be reached for comment.
The extremist group seized the dam on the Tigris River on Aug. 7. Residents near the dam say the airstrikes killed militants, but that could not immediately be confirmed. The residents spoke on condition of anonymity out of fears for their safety.
Tens of thousands of Yazidis fled when the Islamic State group earlier this month captured the northern Iraqi town of Sinjar, near the Syrian border.
The plight of the Yazidis, tens of thousands of whom were stranded on a desert mountaintop for days, encircled by the Islamic extremists, prompted U.S. and Iraqi forces to launch aid drops. It also contributed to the U.S. decision to launch airstrikes against the militants, who were advancing on the Kurdish regional capital Irbil.
Most of those Yazidis were eventually able to escape to Iraq's largely autonomous Kurdish region with the help of Kurdish fighters, and on Thursday Obama said Americans should be proud of the U.S. efforts to save them.
"We broke the ISIL siege of Mount Sinjar, we helped vulnerable people reach safety and we helped save many innocent lives." Obama said, speaking from his vacation spot in Edgartown, Massachusetts. He was referring to the extremist group by its earlier acronym.
But the Islamic State group remains in control of vast swaths of northeastern Syria and northern and western Iraq, and the scale of the humanitarian crisis prompted the U.N. to declare its highest level of emergency earlier this week.
Some 1.5 million people have been displaced by fighting since the Islamic State group's rapid advance across northern and western Iraq began in June.
The decision to launch airstrikes marked the first direct U.S. military intervention in Iraq since the last troops withdrew in 2011, and reflected growing international concern about the extremist group.
On Saturday, Britain's Ministry of Defense said it deployed a U.S.-made spy plane over northern Iraq to monitor the humanitarian crisis and movements of Islamic State militants. It said the converted Boeing KC-135 tanker, called a Rivet Joint, would monitor mobile phone calls and other communication.
Germany's Foreign Minister Frank-Walter Steinmeier was in Baghdad on Saturday, where he announced his government would provide more than 24 million euros ($32.2 million) in humanitarian aid to Iraq.
"The first German air force planes are flying to Irbil at this moment to deliver humanitarian aid," Steinmeier said in a joint press conference with Iraq's acting Foreign Minister Hussein Shahristani.
"In the current situation where minorities, especially in northern Iraq, are expelled and murdered, where children are orphaned and women are enslaved, humanitarian aid is extremely important."
Two British planes also landed Saturday in the Kurdish regional capital Irbil carrying humanitarian supplies.
But Khalil, the Yazidi lawmaker, said the U.S. must do more to protect those fleeing the Islamic State group.
"We have been calling on the U.S. administration and Iraqi government to intervene and help the innocent people, but it seems that nobody is listening," Khalil said.