Suspected Russian airstrikes pounded the rebel-held Syrian city of Idlib killing at least 50 people and leaving dozens more injured and trapped under rubble.
Military jets carried out the bombardment in the early hours of Tuesday striking civilian areas near a hospital and a mosque.
At least five children were among those killed, according to the British-based Syrian Observatory for Human Rights.
Russia's Defense Ministry has denied carrying out any strikes on the city.
"Russia aviation hasn't performed any combat tasks, moreover [it] hasn't conducted any airstrikes in the province of Idlib," military spokesman Igor Konashenkov said in a statement.
Idlib, a provincial capital, is held by the al-Qaida affiliated al-Nusra front which is not signatory to the Russia- and U.S.-brokered cease-fire that went into effect in February.
Moscow has been carrying out an air campaign in support of its Syrian allies since September 2015.