Small arms and light weapons have been sold in Facebook “arms bazaars,” according to a New York Times report.

This week, after the Times provided Facebook with seven examples of suspicious groups, the company shut down six of them, the report says.

Earlier this year Facebook banned the private sale of guns and ammunition on the social network and its Instagram subsidiary.

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The Times based its findings on a study released by Armament Research Services (ARES), which highlights the online trade of light weapons in Libya. The findings are also based on the Times’ own reporting of similar trafficking in Syria, Iraq and Yemen.

The ARES study notes that the 2011 revolution in Libya brought an end to the Libyan state’s regulation of the arms trade. Military stockpiles were raided and small arms and light weapons made their way into the hands of non-state armed groups and private sellers, it added.

“From a virtually non-existent domestic market, the revolution and its aftermath paved the way for a large illicit arms trade to emerge,” said the study. “Many of the players in this new market began to use new technologies to hawk their wares. Online sales via social media platforms are one of the tools currently being used for this purpose.”

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Weapons on sale have included heavy machine guns, shoulder-fired recoilless weapons, rocket launchers, anti-tank guided weapons, grenade launchers and Man-Portable Air Defence Systems (MANPADS), the study says.

Facebook’s Head of Global Policy Management Monika Bickert told the Times that one reported group survived the company’s scrutiny, noting that it displayed photos of weapons but only discussed them and forbade sales.