Russia stepped up its air strikes after a cessation deal with the United States was announced on Monday, as the Syrian opposition council feared worse was yet to come before the deal is due to take effect on Saturday.
High Negotiations Committee (HNC) spokesman Salem al Meslet expressed opposition fears during a meeting in Riyadh saying that Russia will use the deal to target Free Syrian Army (FSA) rebels who fight against Bashar al Assad's regime.
"We fear that Russia” will use the deal to target the moderate factions in Syria," Meslet said, adding some terms of the deal were heavily influenced by Russia.
The cessation deal excludes DAESH and Al Qaeda affiliated Al Nusra Front.
Opposition thinks this will give the regime a pretext to keep attacking them because DAESH and Al Nusra Front hold sway over some of the areas they currently control.
Russia started its air strike campaign backing Assad on September 30, 2015, considered a turning point in the five-year-old civil war.
DAESH terrorists were reported to have tightened their grip on Assad regime supply route to Aleppo on Tuesday, as the regime forces battled to retake the road as a part of their campaign to recapture the city.
Russian air strikes are targeting one of the last avenues into opposition-held areas of Aleppo.
"The escalation in the bombing is targeting areas in Aleppo, in Homs and in Daraya," Muslet said, referring to the town of Daraya southwest of Damascus.
"We expect more than that from the regime and from the Russian raids."
The HNC said on Monday it "consented to" the international efforts but that acceptance of a truce hinged on an end to blockades of rebel-held areas, free access for humanitarian aid, release of detainees, and a halt to air strikes on civilians.
It also said there is no hope of ceasing of hostilities by the regime, Russia or Iran.
"We are studying this truce and we are worried about the obscure points. There is no objection to the truce if it is implemented precisely, without Russia taking it as an excuse to target the moderate revolutionary factions," Muslet said.