"Not only for the Idlib region but for the future of Syria; it will cause catastrophe and the clashes may last a long time", he warned. The ministry also claimed that a private British contractor is helping the rebels stage the attack, according to news agency AFP.
"This provocation with the active participation of the British special services will serve as another pretext for the US, UK and France to conduct a missile strike on the Syrian government and economic facilities", Konashenkov said.
Russian Federation defended its Syrian ally and insisted the Douma attack was staged by the volunteer rescue service known as the White Helmets, which receives substantial funding from the UK Foreign Office and other Western governments.
He voiced concern over the possibility that the Assad regime and Iran could use chemical weapons "as probably this is the only way to carry out such a military attack". "They pose a threat to us first".
The UN peace envoy for Syria will host Iran, Russia and Turkey for talks on drafting a new Syrian constitution on September 11-12.
Foreign ministry spokeswoman Agnes von der Muhll said the conditions for a return have not been met, given Assad's treatment of those who have already gone home and a possible offensive on rebel territory in northern Syria.
Vietnamese community honors McCain with candlelight vigil in Phoenix
McCain died Saturday at his family's ranch near Sedona after battling an aggressive form of brain cancer for over a year. Congressional leaders announced Sunday that they would give one of the highest honors possible to the late Sen.
Russia's Lavrov on Friday called the situation in Idlib "multi-faceted" and called for separating out "the healthy opposition from terrorist structures".
Russia, Turkey and Iran have held talks under the Astana peace process launched past year and agreed to create four "de-escalation" zones to pave the way for a nationwide ceasefire.
The main target is the city of Jisr Al-Shughur in Northwest Idlib province, plateau of al-Haab, the Northern province of Hama and the South-Western part of the province of Aleppo. It borders Turkey to the northwest but is otherwise nearly totally surrounded by regime territory, prompting fears the government would eventually attack it.
Currently, Assad's army is preparing to invade the province of Idlib, which is under the control of the opposition.
As Western-backed moderate Sunni rebels have surrendered or retreated in the previous year, Washington appears to have given up on its longtime goal of toppling Assad and has focused on two other objectives: stopping any further use of chemical weapons by Assad and curbing Iranian influence in Syria.
In the same interview Assad said rescue workers from the White Helmets group would be killed if they did not turn themselves in.
Moscow will continue to support Damascus in its efforts to stabilize the situation in Syria, including in the return of refugees and internally displaced persons (IDPs), the diplomat emphasized.