Picture for representational purposes only.
More than 40 of Syria's most powerful rebel factions said today that Russia's air campaign had made a political solution to the country's bloody conflict impossible.
In a statement posted online, 41 groups including Jaish al-Islam near Damascus, Ahrar al-Sham in northwest Syria, and the Northern Front said that Russia's "brutal occupation has cut the road to any political solution".
The statement also urged the creation of a regional coalition to combat both the Syrian regime and its allies Iran and Russia.
Russian warplanes have been flying over Syrian territory since Wednesday, conducting air strikes on what Moscow says are Islamic State group targets in the northern and central provinces.
Although some of the raids have struck IS bastions in Raqa and Homs provinces, many have hit bases held by other rebel and Islamist groups.
Some of the statement's signatories, like Ahrar al-Sham and Jaish al-Izzah, have been targeted by Russian strikes.
"Russia jumped in to rescue the Assad regime after it was clinically dead, in order to prevent it from suffering a sweeping defeat," the statement read.
It accused Russia of killing at least 50 civilians in Homs province "in Russia's first war crime on Syrian territory".
The statement also called for an international coalition to help fight back at the Syrian regime and its two steadfast allies, Iran and Russia.
"This new reality makes it imperative that regional countries, and allies in particular, hasten to form a regional alliance in the face of the Russian-Iranian alliance of occupation," the groups wrote.
It followed a statement at the weekend by many of the same rebel groups and the opposition National Coalition "rejecting Russia's direct military escalation in Syria".
"This escalation undoubtedly proves that Russia was not serious or genuine in its commitment to a political process, and that it cannot be an impartial intermediary because it is party to the conflict."
Syria's conflict began as an uprising against the rule of President Bashar al-Assad, but has transformed into a multi-party civil war with Kurds, the regime, rebels and jihadists carving out zones of influence.
Russia and Iran have provided substantial financial and military aid to Damascus.