British guns are being advertised for sale on Facebook in Libya, where thousands of Islamic State fighters are to be active.
Rifles, light machine guns and revolvers are among the firearms listed in secret trading groups on the social network, even though Facebook has a strict policy against such transactions.
Once a buyer finds a weapon, deals are negotiated through private messages and phone calls – with some sub-machine guns being sold for as little as £400.
The Times said photographs and detailed descriptions of the guns were discovered by Armanent Research Services (ARES), which provides intelligence to governments on the use of arms and munitions.
Among the guns it reported being for sale were a Bren light machine gun, which was standard issue for British forces in World War Two, and a Sterling sub-machine gun which was used by the British Army from the 1950s to the 1990s.
Nic Jenzen-Jones, a director of ARES, told the newspaper that the British weapons being sold could have been exported directly to the Libyan government before the rise of Muammar Gaddafi.
British handguns are also among those being sold on Facebook, it is claimed – and David Dyson, an independent firearms expert, believes some of those weapons may have been left behind in North Africa by British troops after the conflict ended.
Facebook has said sales pages which violate its rules have been removed in light of the group’s findings.
A report released by the Small Arms Survey suggested that sales of weapons on the black market in Libya are a new development – as the internet only became widely available in the country following the fall of the Gaddafi regime in 2011.
The Geneva-based research organisation said arms traders had “quickly realised the viability of social media for expanding their access to potential customers”.
Facebook said: “It’s against Facebook’s community standards to co-ordinate private sales of firearms, and we remove any such content as soon as we become aware of it.
“We encourage people to use the reporting links found across our site so that our team can review content swiftly.”