Civilian aircraft flying in or out of airports in the Syrian cities of Damascus or Aleppo risk being shot down from 10 September onwards, opposition group the Free Syrian Army has publicly declared.
"The airports of Damascus and Aleppo will be considered legitimate targets as of 10 September," says the group's political advisor, Bassam El-Dada.
Speaking on France 24's Arabic channel, he accused the Syrian regime of having "transformed these airports into platforms that serve to transport troops and refill arms and ammunition via Syrian, Iranian and Russian civilian airplanes."
El-Dada blames the regime for the Free Syrian Army's actions, saying: "The responsibility for what happens now is back in the hands of the illegitimate regime of Syria, as well as its Russian allies ... If we were irresponsible, we would not have warned the civilian airlines."
Etihad recently withdrew services from the war-torn Syrian capital Damascus, joining other airlines such as Aeroflot, Air France-KLM and Royal Jordanian Airlines.
Figures from the Arab Air Carriers Association show that in June 2012 only 117 weekly flights operated to and from Syria, compared to 505 during the same period in 2011. Services were conducted by 14 different airlines this year, compared to 33 carriers in June 2011.
Syrian Arab Airlines were unavailable for comment on the issue.