A squad of U.S. troops despatched by helicopter across the Libyan desert to rescue besieged diplomats from Benghazi on Wednesday ran into a fierce overnight ambush that left a further two Americans dead, Libyan officials told Reuters.

Accounts of the mayhem at the U.S. consulate, where the ambassador and a fourth American died after a chaotic protest over a film insulting to Islam, remain patchy. But two Libyan officials, including the commander of a security force which escorted the U.S. rescuers, said a later assault on a supposedly safe refuge for the diplomats appeared professionally executed.

Miscommunication which understated the number of American survivors awaiting rescue – there were 37, nearly four times as many as the Libyan commander expected – also meant survivors and rescuers found themselves short of transport to escape this second battle, delaying an eventual dawn break for the airport.