Al-Qaeda on Thursday threatened the imminent execution of an American journalist it kidnapped in Yemen, mocking as "foolish" a failed bid by US forces to free him.
Al-Qaeda in Yemen released a video dated December 2014 naming the hostage as Luke Somers, 33, saying the photojournalist was kidnapped more than a year ago in Sanaa.
US-based monitoring agency SITE Intelligence Group said Somers was seized in the Yemeni capital in September 2013.
Nasser bin Ali Al-Ansi, of Al-Qaeda in the Arabian Peninsula (AQAP), threatened in the video to kill Somers in three days if Washington fails to meet unspecified demands.
The Yemeni defence ministry said last week that Al-Qaeda had moved hostages, including a US journalist, a Briton and a South African, days before a raid in southeastern Hadramawt province to free the American.
Ansi mentioned a "failed operation" in Hadramawt in which militants died, describing it as the "latest foolish action" by the United States.
The United States said on Thursday that American and Yemeni forces recently tried to rescue Somers.
"Regrettably, Luke was not present, though hostages of other nationalities were present and were rescued," said National Security Council spokeswoman Bernadette Meehan.
The White House said President Barack Obama had approved a rescue operation last month.
- Raid by Navy SEALs -
Details of the operation were classified but Defence Department spokesman Rear Admiral John Kirby echoed Meehan, saying some hostages had been rescued but that Somers was "not present at the targeted location".
The New York Times reported that US special operations forces found eight other hostages in the raid.
About two dozen commandos from the US Navy's SEALs, joined by a small number of Yemeni troops, flew by helicopter to a location near the Saudi border, the Times reported, citing US and Yemeni officials.
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The SEALs then walked several hundred metres (yards) at night to a mountain cave, taking Al-Qaeda militants by surprise, it said.
Kirby said Washington would work relentlessly to "bring people home whenever we can.
"The United States will not tolerate the abduction of our people, and will work tirelessly to secure the safety of our citizens and to hold their captors accountable."
Meehan said the rescue operation "should serve as another signal to those who would do us harm that the United States will not tolerate the abduction of our people, and will spare no effort to secure the safe return of our citizens and to hold their captors accountable.
"Our thoughts remain with the Somers family, and with the families and loved ones of every other US citizen being held hostage overseas," she added.
- Qaeda executions uncommon -
Hundreds of people have been kidnapped in Yemen during the past 15 years, mostly by tribesmen who use them as bargaining chips in disputes with the government.
Nearly all have been freed unharmed.
While AQAP is considered by Washington as the most dangerous affiliate of Al-Qaeda, it is not known for frequently executing foreign hostages.
Its threat follows the murder of five Western hostages since August by the Islamic State group that controls parts of Syria and Iraq.
Two US journalists, James Foley and Steven Sotloff, American aid worker Peter Kassig, and British aid workers Alan Henning and David Haines were executed.
Yemen is a key US ally in the fight against Al-Qaeda, allowing Washington to conduct a longstanding drone war against the group on its territory.
The militant group has exploited instability in the impoverished country since a 2011 uprising forced president Ali Abdullah Saleh to step down.
And in recent years there has been a growing number of abductions by Al-Qaeda, several of whose hostages remain in captivity.
They include a South African teacher and two diplomats, one from Iran and the other from Saudi Arabia.