US photojournalist Luke Somers and South African teacher Pierre Korkie have been killed during a rescue attempt by US and Yemeni forces.

The pair were murdered by their Al Qaeda captors - 10 of whom were also killed - during the raid in the Shabwah region of Yemen, the US said.

There are reports the South African hostage was due to be released tomorrow - but President Barack Obama authorised the raid because information "indicated that Luke's life was in imminent danger".

"Based on this assessment, and as soon as there was reliable intelligence and an operational plan, I authorised a rescue attempt," Mr Obama said.

"I also authorised the rescue of any other hostages held in the same location as Luke."

Yemen's national security chief, Ali al-Ahmadi, said the militants planned to "execute" Mr Somers - who was born in Britain - on Saturday.

The death of Mr Korkie was confirmed by the disaster relief group Gift of the Givers.

"The psychological and emotional devastation to [his wife] Yolande and her family will be compounded by the knowledge that Pierre was to be released by Al Qaeda tomorrow," the organisation said.

"It is even more tragic that the words we used in a conversation with Yolande at 5.59 this morning was 'the wait is almost over'. Three days ago we told her Pierre will be home for Christmas."

Mr and Mrs Korkie were taken hostage by Al Qaeda in the Arabian Peninsula (AQAP) in May 2013 - though Yolande was released at the start of this year.

Luke Somers

Mr Somers was captured in September last year.

Militants released a video on Wednesday threatening to kill him within three days if their demands were not met.

The 33-year-old appeared in the footage saying he feared for his life.

Following the rescue attempt US troops took Mr Somers to a naval ship but he was reportedly dead upon arrival.

His sister, Lucy Somers, has asked that "all of Luke's family members be allowed to mourn in peace".

Ms Somers had posted a YouTube video pleading for her brother's release just hours before his death.

The raid was the second attempt to free Mr Somers.

Mr Obama condemned his murder as "barbaric".

"Luke was a photojournalist who sought through his images to convey the lives of Yemenis to the outside world," he said.

"The callous disregard for Luke's life is more proof of the depths of AQAP's depravity, and further reason why the world must never cease in seeking to defeat their evil ideology."

News of the failed rescue comes after a suspected US drone strike killed nine alleged Al Qaeda militants in Shabwah overnight.

Originally posted at 10.45am