An investigation by The Times newspaper found that several of the Yemeni accounts bore the blue tick of verification.
Both The Times and the BBC have approached X for comment, but have not so far received any response.
Most of the platform’s content moderators were laid off after the new owner Elon Musk bought the company in 2022.
The advertisements are mostly in Arabic and aimed primarily at Yemeni customers in a country where the number of guns is often said to outnumber the population by three to one.
The BBC has found several examples online, offering weapons at prices in both Yemeni and Saudi riyals.
The words beside the weapons are designed to lure in the buyers.
“Premium craftsmanship and top-notch warranty,” says one advertisement. “The Yemeni-modified AK is your best choice.”
A demonstration video, filmed at night, shows the seller blasting off a 30-round magazine on full automatic.
Another offers sand-coloured Pakistani-produced Glock pistols for around $900 each.
Yet these advertisements are not hidden in the depths of the Dark Web, where guns and other illegal items are usually traded, they are in plain sight on X, openly accessible to millions of people.
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