Syrian activists raised on Tuesday the death toll from the late night airstrikes on the northwestern city of Idlib, saying at least 23 people were killed.

The Britain-based Syrian Observatory for Human Rights said that Russian aircraft carried out the strikes, which pummeled the city, despite Moscow’s denial.

“Russian planes did not carry out any combat missions, to say nothing of any air strikes, in the province of Idlib,” Igor Konashenkov, a Russian Defense Ministry spokesman, said in a statement.

Idlib is held by several militant groups, including al-Nusra Front. Another activist group, the Local Coordination Committees, gave a higher toll, saying the airstrikes killed 50.

Since the Russian military campaign began last September in an effort to shore up Bashar Assad’s forces in their battle against militants, Moscow has staunchly denied that its warplanes have hit any civilian areas in Syria.

Konashenkov called the Observatory’s allegations “a horror story” of the kind he said it had disseminated in the past and said such pronouncements should be regarded with greater skepticism.

The Turkish foreign ministry said the strikes had killed more than 60 civilians and injured around 200 people.

In an e-mailed statement, the ministry called on the international community to act swiftly against what it called the “indefensible” crimes of the Russian and Syrian regime.

Meanwhile, U.S.-backed Kurdish-led fighters have seized ground from ISIS in Syria, the Observatory said.

The Syrian Democratic Forces, who control a swathe of territory along the Turkish border, launched a push south towards the ISIS stronghold of Raqqa last week, capturing a string of villages in the north of Raqqa province.

“The SDF has captured 12 villages… northwest of Raqqa in the past 36 hours,” Observatory chief Rami Abdel Rahman said.

He said that the villages lie 80 kilometers or more from Raqqa itself but that the jihadists’ de facto Syria capital was not the immediate goal.

He said the target of the offensive was the town of Tabqa and its adjacent dam on the Euphrates River, which lie some 40 kilometers upstream.

ISIS lost 18 fighters in the fighting on Monday, taking its losses since the start of the offensive on May 24 to 79, he said.

Among those killed were 24 child fighters from ISIS’s “Cubs of the Caliphate” recruitment program.