The United States on Thursday for the first time publicly disclosed a failed attempt last month to rescue a U.S. citizen held hostage by al Qaeda's Yemen branch, and the group threatened to kill him in a new video posted on the Internet.

U.S. officials said President Barack Obama last month authorized a secret raid to rescue Luke Somers, a 33-year-old journalist who was kidnapped in Yemen's capital Sanaa in September 2013. Somers was not at the targeted location, although other hostages were freed, the officials said.

"As soon as the U.S. government had reliable intelligence and an operational plan, the president authorized the Department of Defense to conduct an operation to recover Mr. Somers," said Bernadette Meehan, a spokeswoman for the White House National Security Council. "Regrettably, Luke was not present."

Pentagon spokesman Rear Admiral John Kirby said the rescue operation was carried out in partnership with Yemen's military and involved air and ground components.

"Details about the mission remain classified," Kirby said.

In the assault on a cave in remote Hajr as-Say'ar district in the eastern province of Hadramout, U.S. and Yemeni security forces rescued six Yemenis, a Saudi and an Ethiopian, and killed seven al Qaeda kidnappers, Yemeni officials said previously.

The Yemeni defense ministry's 26sept.net website later quoted a soldier who had participated in the rescue as saying an American, a Briton and a South African held there had been moved elsewhere two days earlier.

The U.S. disclosure came after the appearance of a new video by al Qaeda in the Arabian Peninsula (AQAP), the militant network's Yemen arm, purporting to show Somers and threatening to kill him if unspecified demands were not met.

The man identifying himself as Somers said he was looking for "any help that can get me out of this situation."

Reuters was unable to confirm the authenticity of the video, posted on YouTube and social media late on Wednesday and carried by SITE, an organization that monitors militant statements.

The man in the video says he was born in the United Kingdom and holds American citizenship.

"We give the American government a timeframe of three days from the issuance of this statement to meet our demands about which they are aware; otherwise, the American hostage held by us will meet his inevitable fate," an AQAP official identified as Nasser bin Ali al-Ansi said in the video.

World Bulletin.