As many as 117 civilians have been killed in drone and other counterterror attacks in Pakistan, Yemen and elsewhere during President Barack Obama's presidency, according to a report released late on Thursday by US intelligence officials.
It was the second public assessment the Obama administration has issued in response to mounting pressure for more information about lethal US operations overseas.
Human rights and other groups have criticised the administration, saying it has undercounted civilian casualties.
They also are worried that President-elect Donald Trump will more aggressively conduct drone strikes, which are subject to little oversight from Congress or the judiciary.
The reports by National Intelligence Director James Clapper said the US conducted 526 counterterror strikes, including those by unmanned drones, between January 2009 and December 2016.
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The reports do not mention where the strikes occurred, but the Defence Department and CIA have pursued targets in Pakistan, Yemen, Somalia and Libya.
The data didn't include strikes in Iraq, Syria and Afghanistan, which the US considers areas of active hostilities.
Between 2,803 and 3,022 combatants were killed in strikes during Obama's eight-year presidency, according to the reports. Between 64 and 117 non-combatants were killed.
Non-governmental organisations have estimated that hundreds more have been killed.
Senior US officials have cited several reasons for the discrepancy, including the government's access to sensitive intelligence that helps it more accurately identify the deceased.
Human rights groups say some of the discrepancies in conflicting numbers could be cleared up if the government disclosed the names of civilians killed and the dates, locations and other details about the strikes.
In a speech earlier this year, Obama acknowledged critics who don't support the drone program, but he said they need to weigh the alternatives.
"Drone strikes allow us to deny terrorists a safe haven without air strikes, which are less precise, or invasions that are much more likely to kill innocent civilians as well as American service members," Obama said.
Trump has not addressed the drone policy specifically, but he has said he wants to "take out terrorists" and expects he will continue using drones in counterterror operations.
