President Barack Obama on Saturday condemned the murder of US journalist Luke Somers who was killed in Yemen during a failed raid aimed at freeing him from his Al-Qaeda kidnappers.

President Barack Obama on Saturday condemned the murder of US journalist Luke Somers who was killed in Yemen during a failed raid aimed at freeing him from his Al-Qaeda kidnappers.

"The United States strongly condemns the barbaric murder of Luke Somers at the hands of Al-Qaeda terrorists during a rescue operation," Obama said in a statement. "I offer my deepest condolences to Luke's family and to his loved ones."

Obama also offered support to the family of another hostage, identified as South African Pierre Korkie, who was killed alongside Somers a day before he was due to be freed after more than a year in captivity, according to a charity negotiating his release.

"I also offer my thoughts and prayers to the family of a non-US citizen hostage who was also murdered by these terrorists during the rescue operation. Their despair and sorrow at this time are beyond words," Obama said.

Somers appeared in a video this week saying his life was in imminent danger and appealing for help, while his captors also released a video threatening to kill the 33-year-old British-born US citizen, who has been held captive for more than a year.

Obama said the captives' deaths would not deter his government's attempts to secure American hostages and fight its enemies.

"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.

"Terrorists who seek to harm our citizens will feel the long arm of American justice," Obama vowed.

The White House said the rescue operation had been carried out in cooperation with the Yemeni government, which 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.