"The US took napalm out of service in the 1970's. We completed the destruction of our last batch of napalm on April 4, 2001, and no longer maintain any stocks of napalm," Commander Davis told smh online. He was apparently referring to Vietnam-era Napalm-B, which consisted of inflammable fuel thickened with polystyrene and benzene.

The inflammable fuel in Mark-77 fire bombs is thickened with slightly different chemicals, and is believed to contain oxidizers, which make it harder to extinguish than Napalm-B.

Neither weapon technically contains napalm. The chemical mixture that became known as 'napalm' - a combination of naphthalene and palmitate - was used only in the earliest versions of the weapon.

Napalm was banned by United Nations convention in 1980, but the US never signed the agreement. Use of Mark-77 fire bombs is considered legal by the US military.

Ms. Toni McNeal, a spokesperson for Rock Island Arsenal, in Illinois, said the facility is currently producing a further 500 Mark-77s for the US Marine Corps.

She said she did not consider the Mark-77s to be napalm bombs.

But Mark-77s are referred to as 'napalm' in some current US inventories and public affairs documents.

A US Navy public affairs document dated 22/10/99 says that the US Navy no longer uses napalm but "the US Marine Corps has a requirement and uses it at ranges at Yuma and Twenty-Nine Palms."

Twenty-Nine Palms, in California, is the home base of some of the Marine Corps units that took part in the attack on Safwan Hill in Iraq.

Captain Robert Crum, USMC, Public Affairs spokesman for Twenty-Nine Palms, said: "Mk 77s are not routinely used in training at 29 Palms. Yet it would be inappropriate to say that they are never - or never would be - used in training here.

"The average young Marine may be unfamiliar with the technical nomenclature, and probably does refer to this munition by the vernacular 'napalm'."