WASHINGTON (AFP) - President Barack Obama revealed on Thursday that an American and an Italian hostage were accidentally killed in a covert US counter-terrorism operation near the Afghan-Pakistan border in January, taking "full responsibility" for the tragedy.
A senior Al-Qaeda leader, an American, was also killed in the operation and the group's English-language spokesman, US convert Adam Gadahn, died in a separate strike.
Lifting the lid on a previously classified finding, a solemn Obama expressed his "deepest apologies" to the families of 73-year-old economic advisor Warren Weinstein and aid worker Giovanni Lo Porto, 39.
Obama gave few details of the operation, which officials suggested was a drone strike that took place against an Al-Qaeda compound inside Pakistan.
"As president and as commander-in-chief, I take full responsibility for all our counter-terrorism operations, including the one that inadvertently took the lives of Warren and Giovanni," he said.
"I profoundly regret what happened. On behalf of the United States government, I offer our deepest apologies to the families.
"It is a cruel and bitter truth that in the fog of war generally and our fight against terrorists specifically, mistakes - sometimes deadly mistakes - can occur."
Obama said he informed Italian Prime Minister Matteo Renzi personally about his administration's findings.
Italy's foreign ministry described the deaths as a "tragic and fatal error by our US allies" but said "terrorists" were entirely to blame.
But this is just the latest controversy around Obama's counter-terrorism operations, which - while killing Osama bin Laden in a commando raid - have more often relied heavily on secret drone strikes.
Obama was quick to stress that "we do believe that the operation did take out dangerous members of Al-Qaeda."
The White House said that Ahmed Faruq, an American described as a leader of Al-Qaeda in the Indian Subcontinent, was killed in the incident.
Another operation at around the same time in the same area killed Gadahn, a Californian who converted to Islam as a teenager and later travelled to Pakistan, becoming an Al-Qaeda spokesman and being indicted for treason.
The White House said neither man was specifically targeted.
"Since 9/11, our counterterrorism efforts have prevented terrorist attacks and saved innocent lives both here in America, and around the world," Obama said.
FACE THEIR GOD
Despite Obama's defense of his counter-terrorism record, Congressional leaders rapidly called for more oversight over the drone programme.
Democratic Senator Dianne Feinstein demanded an "annual report on the number of deaths, both combatant and civilian, from US strikes."
Republican Senator John McCain said there must be a review of the incident, but indicated the drone program should continue.
"These new disclosures raise troubling questions about the reliability of the intelligence that the government is relying on to justify drone strikes," said American Civil Liberties Union deputy legal director Jameel Jaffer.
"In each of the operations acknowledged today, the US quite literally didn't know who it was killing."
Weinstein was snatched after gunmen tricked their way into his home in Lahore on August 13, 2011 shortly before he was due to return home after seven years working in Pakistan.
He later appeared in a video in which, under apparent coercion, he asked the United States to free Al-Qaeda prisoners.
Weinstein's widow said in a statement that "we are devastated by this news and the knowledge that my husband will never safely return home."
"The cowardly actions of those who took Warren captive and ultimately to the place and time of his death are not in keeping with Islam and they will have to face their God to answer for their actions," she said.
Lo Porto disappeared in January 2012 in Pakistan, just a few days into his second stint in the country. A native of Sicily, Lo Porto previously worked in Croatia, the Central African Republic and Haiti.
The White House said the United States would compensate the families' of both men, but details have yet to be finalised.