US-supplied weapons ended up for sale on an online terrorist marketplace in Syria.

"Grenade launchers, heavy machine guns, thermal sniper scopes and body armor all appear on the jihadist channels, which also offer tips on encryption and even introduce smugglers to get people in and out of Syria," the CNN report said.

The media outlet also published a string of messages between someone in Syria’s Idlib province and a reporter, in which the reporter negotiated a discount to purchase the M-16 rifle for $775 using the encryption app Telegram.

The rifle carries a serial number that small arms experts say matches a batch originally thought to have been given to Iraqi security forces by a US assistance program, but that was found in possession of ISIS terrorist group (banned in Russia) in 2014, the report said.

US and Saudi Arabia has been arming military groups committed to overthrowing the government of President Bashar al-Assad since September 2011. This flood of weapons into Syria, along with the entry of 20,000 foreign fighters into the country—primarily through Turkey—largely defined the nature of the conflict.