US officials Sunday defended President Barack Obama's decision to launch a special forces rescue operation in Yemen that ended with Al-Qaeda killing an American photojournalist and a South African teacher.
Saturday's US commando raid to free 33-year-old American Luke Somers came two days after the kidnappers had issued a video in which they threatened to kill him within 72 hours.
But it also came a day before the South African hostage, 57-year-old Pierre Korkie, had been due to be released under a negotiated deal.
Calling the murders "barbaric," Obama said he had authorised the rescue attempt because the video and other information "indicated that Luke's life was in imminent danger".
"The United States will spare no effort to use all of its military, intelligence, and diplomatic capabilities to bring Americans home safely, wherever they are located," he said.
The South African government said Sunday it was "deeply saddened" by the killing of Korkie.
It said in a statement that it had undertaken "numerous initiatives... to help secure Mr Korkie's release."
A top US lawmaker said Sunday he agreed with the president's decision to carry out the raid.
"The intelligence was good," Mike Rogers, chairman of the House Intelligence Committee, told CNN television.
US Defence Secretary Chuck Hagel said there had been "compelling reasons to believe Somers's life was in imminent danger".
A senior defence official said: "It was either act now and take the risk, or let that deadline pass. And no one was willing to do that."
British-born Somers had worked as a freelance photographer for the BBC and spent time at Yemeni newspapers before being abducted in Sanaa in September 2013.
- 'Lost element of surprise' -
Korkie and his wife Yolande, who had worked as teachers in Yemen for four years, were kidnapped by Al-Qaeda in the Arabian Peninsula (AQAP) in May 2013.
She was released in January and the Gift of Givers charity said logistical arrangements had already been put in place to fly Korkie out of Yemen on Sunday.
Saturday's operation saw 40 US commandos dropped by helicopter 10 kilometres (six miles) from where Somers and Korkie were being held in the southeastern province of Shabwa, officials said.
They made their way to the Al-Qaeda hideout by foot, but were discovered about 100 metres (yards) away.
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A short but intense firefight erupted, the US defence official said.
"When the element of surprise was lost, and a firefight ensued, we believe that is when (the hostages) were shot," the official said.
One hostage -- it was not clear who -- had died en route to the USS Makin Island off Yemen, and the other died on the operating table.
The defence department said the operation had been conducted with the "assistance and cooperation" of Yemen's government and security forces.
Yemen said 10 militants died and four members of its security forces were wounded.
- 'Home for Christmas' -
Friends and family described Somers as a committed journalist who sought to document the lives of ordinary people amid turmoil.
Yemen has been wracked by unrest since a 2011 uprising forced president Ali Abdullah Saleh to resign, with rival militias battling for control of parts of the impoverished country.
Korkie's family had been expecting him home soon, said the Gift of Givers charity, which had been negotiating his release.
"The psychological and emotional devastation to Yolande and her family will be compounded by the knowledge that Pierre was to be released by Al-Qaeda tomorrow," it said.
"Three days ago we told her 'Pierre will be home for Christmas'."
A US official said Washington had been aware two hostages were at the location but did not know the identity of the second.
The threat to kill Somers followed the murders of five Western hostages since August by the jihadist Islamic State group in Syria and Iraq.
Experts said the deaths during the raid were likely the result of intelligence failures.
Mustafa Alani, a security analyst from the Geneva-based Gulf Research Centre, said there appeared to have been a lack of information "on the area where the hostages were being held and the movements of the kidnappers".
AQAP, considered one of the group's most dangerous affiliates, launches frequent attacks in Yemen and has also organised a series of attempted bomb attacks on Western targets.
It is believed to be holding several other foreign hostages, including a Briton and Saudi and Iranian diplomats.