US officials have confirmed that elite US Navy Seals were dropped into Somalia to carry out the overnight operation which resulted in a shoot-out.
Vice-President Joe Biden told ABC News that the mission had been approved because of the failing health of one of the aid workers.
The hostages – a US woman and a Danish man – were seized on 25 October.
American Jessica Buchanan, 32, and Dane Poul Thisted, 60 were freed uninjured, although nine of their captors are said to have been killed. No casualties have been reported among US forces.