BEIRUT -- Prosecutors in southern Turkey have alleged that Syrian rebel groups were seeking to buy materials that could be used to produce highly toxic sarin gas, Turkish media reported Friday.
An indictment issued in the southern city of Adana alleged that a Syrian national identified as Hytham Qassap, 35, was in Turkey trying to procure chemical materials for a pair of well-known Islamist rebel blocs, Al Nusra Front and the Ahrar al-Sham Brigades, the reports said. Washington has designated Al Nusra Front as a terrorist group linked to Al Qaeda.
Neither group is affiliated with the U.S.-backed Free Syrian Army.
Five other suspects, all Turkish citizens, were indicted in the case, Turkish media reported. All six suspects have pleaded not guilty, according to the English-language Hurriyet Daily News, which quoted from the indictment.
The alleged ring never manufactured sarin, a potent nerve agent, according to Turkish media.
The investigation began with a tip to police that some Syrian rebel groups might be seeking to obtain materials in Turkey to produce chemical weapons, the reports said. In May, Turkish police arrested 11 suspects in connection with the case. Turkish officials denied as erroneous some initial reports that sarin had been seized as part of the investigation.
The Turkish-Syrian border, which stretches more than 500 miles, has long been a conduit for arms and manpower destined for the Syrian rebels.
Syrian authorities have repeatedly cited the Adana arrests to bolster their allegation that it is the armed opposition, not their own military, that has mounted poison gas attacks, including the Aug. 21 incident outside Damascus that left hundreds dead.
Russia, Syria's close ally, has alleged that the opposition has created a chemical weapons "cottage industry," designed to frame the Syrian government and prompt Western intervention in the civil war.
The United States and its allies say the proof is overwhelming that it was forces loyal to Syrian President Bashar Assad who unleashed sarin outside Damascus on Aug. 21 and in several previous, smaller-scale attacks elsewhere in Syria.
On Friday, Louay Mekdad, spokesman for the U.S.-backed Syrian National Coalition, said via telephone from Turkey that his group had "no connection" to the Adana case, and he repeated denials of charges that the opposition possesses chemical weapons.
The Syrian government may be behind the criminal case in an undercover bid to discredit the rebels, Mekdad said.
"We do not rule out that this may be a false flag operation, an intelligence operation of the regime," the opposition spokesman said.