Lucy Somers told The Associated Press that she learned of her 33-year-old brother Luke Somers' death from FBI agents. There was no immediate comment from Washington, nor from security officials in Yemen's capital, Sanaa.
"We ask that all of Luke's family members be allowed to mourn in peace," Lucy Somers said.
Yemen's local al-Qaida branch, Al-Qaida in the Arabian Peninsula, posted a video Thursday that showed Somers, threatening to kill him in three days if the United States didn't meet the group's demands, which weren't specified. He was kidnapped in September 2013 from Sanaa.
The news of the failed rescue comes after a suspected U.S. drone strike in Yemen killed nine alleged al-Qaida militants early Saturday, a security official said. The drone struck at dawn in Yemen's southern Shabwa province, hitting a suspected militant hideout, the official said. The official did not elaborate and spoke on condition of anonymity as he wasn't authorized to brief journalists.
At least six suspected militants were killed in an airstrike in the same province last month. Later Saturday, tribal leaders said they saw helicopters flying over an area called Wadi Abdan in Shabwa province.
American authorities rarely discuss their drone strike campaign in Yemen. The strikes are incredibly unpopular in Yemen due to civilian casualties, legitimizing for many the attacks on American interests.
In an online video released Saturday, Lucy Somers described her older brother as a romantic who "always believes the best in people." She ended with the plea: "Please let him live."
In a statement, Somers' father, Michael, also called his son "a good friend of Yemen and the Yemeni people" and asked for his safe release.
In a statement Thursday, Pentagon press secretary Rear Adm. John Kirby acknowledged for the first time that a mysterious U.S. raid last month had sought to rescue Somers but that he turned out not to be at the site.
Kirby did not elaborate on the joint U.S-Yemeni operation to free Somers, saying details remained classified. However, officials have said the raid targeted a remote al-Qaida safe haven in a desert region near the Saudi border. Eight captives — including Yemenis, a Saudi and an Ethiopian — were freed. Somers, a Briton and four others had been moved days earlier.
Somers was kidnapped in September 2013 as he left a supermarket in the Yemeni capital, Sanaa, said Fakhri al-Arashi, chief editor of the National Yemen, where Somers worked as a copy editor and a freelance photographer during the 2011 uprising in Yemen.
The U.S. considers Yemen's al-Qaida branch to be the world's most dangerous arm of the group as it has been linked to several failed attacks on the U.S. homeland.