These were the first attacks of their kind in the area, where no ISIS presence had been noted in more than a year, Mr Abdel Rahman said.
Rescue workers were still searching under the rubble for survivors.
Violent clashes were ongoing in Albu Kamal, which lies in the Euphrates Valley in eastern Syria, the Syrian Observatory for Human Rights monitoring group said.
Russian Federation started participating in anti-terrorist operation in Syria in September 2015 at the invitation of Syrian President Bashar al-Assad, predominantly with missile strikes in support of the Syrian army.
Reports about "the alleged strikes carried out by Russian aircraft in the evening of June 7 near the settlement of Zardana in the Idlib province are untrue", the ministry said Friday in a statement carried by state media.
Northwestern Idlib is the most populated part of Syria which is still under the control of insurgents fighting Bashar al-Assad's government which has the backing of Russian Federation and Iran and has allegedly targeted its own people, even through the use of poisonous gas.
Government airstrikes in Syria have been relatively uncommon in recent months in the rebel-held province, which is part of a de-escalation zone agreed on previous year by Russia, Turkey and Iran. According to the Observatory, at least 45 government and allied forces were killed in the offensive, mostly members of Shia militia groups from Iraq and elsewhere. He said: "Our troops will stay in Syria as long as it is beneficial to Russia".
On Thursday, IS jihadists also killed 22 pro-regime fighters in surprise attacks in the southern province of Sweida, a monitor said.