The father and sister of a US photojournalist taken hostage by al-Qaeda in Yemen have appealed to his captors to spare his life, adding to other public appeals to the group.

Luke Somers, 33, was kidnapped in September 2013 in the Yemeni capital of Sanaa, where he had been working as a freelance photographer for the Yemen Times.

In a video posted on Saturday, Lucy Somers, speaking from near London, described her older brother as a romantic who "always believes the best in people".

"When foreign nationals were advised to leave Yemen, Luke refused to go, saying he felt safe and at home there," Lucy Somers said. "He felt the Yemeni people would look after him."

"Photojournalism has been his way of highlighting the struggles of the Yemeni people," she said.

"Please let him live," she said at the end of her plea.

In a statement released on Saturday, Somers' father Michael called his son "a good friend of Yemen and the Yemeni people" and asked for his safe release.

Michael Somers said his son "was confident that no one would harm him for his simplicity and honest friendship to all Yemenis around him."

Luke Somers "told all his friends and loved ones stories of Yemenis' generosity, humility and devoted friendship," his father added.

Somers' brother, Jordan, and mother, Paula, offered a similar message in an earlier video.

Somers had pleaded for help in a video posted on Thursday on the Twitter account of al-Qaeda in the Arabian Peninsula. The group gave the US three days to meet its demands, failing which it said the "hostage will meet his inevitable fate".

In a statement on Thursday, Pentagon press secretary Rear Adm. John Kirby acknowledged for the first time that a raid last month had sought to rescue Somers but that he turned out not to be at the site that was targeted.

White House spokeswoman Bernadette Meehan also said President Barack Obama had authorised a rescue operation to free Somers and other hostages but "regrettably, Luke was not present."

Meanwhile, a Yemeni security official said at least eight alleged al-Qaeda fighters were killed overnight by an attack conducted by a US drone on the southern province of Shabwa amid the search for Somers.    

Source: Agencies