An American, a Briton and a South African were among several hostages Yemeni forces sought to free from al Qaeda this week, the defence ministry said on its website, describing a raid that a US defence official said also involved US special forces.

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

Late on Wednesday the defence ministry's 26sept.net website 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.

Another foreign hostage, who may have been of Turkish nationality, was also apparently moved along with the three, the soldier was reported as saying. The soldier cited the rescued hostages for that information, the website said.

While al Qaeda-linked gunmen in Yemen are known to be holding a number of foreign hostages, an American had not previously been reported among them.

There was no word on the identity of the Briton or the South African. South Africa has said one of its nationals, Pierre Korkie, a teacher, was being held in Yemen after gunmen kidnapped him in mid-2013.

US officials say al Qaeda in the Arabian Peninsula (AQAP) has funded its operations with millions of dollars in ransoms received for European hostages.

"Intelligence information had become available that al Qaeda was holding 11 hostages who had been seen being transported in a ... vehicle covered in blankets," the website quoted the soldier, identified as Abu Maarouf, as saying.

Only the eight hostages rescued were found at the end of the operation, the soldier said. Yemen officials have made no reference to any participation by foreign forces in the rescue operation.

But in Washington, a US official confirmed participation of US special operations forces, and a second US official acknowledged US military support.

Yemen, which borders the world's top oil exporter, Saudi Arabia, is home to AQAP, which Washington regards as one of the most active branches of the network founded by Osama bin Laden.

The Pentagon said in 2012 the United States had resumed on-the-ground military training to bolster Yemen's fight against al Qaeda.

Kidnapping is common in Western-backed Yemen, which is battling not only an al Qaeda insurgency but also a southern separatist movement and sporadic conflicts with armed tribes.