Scores of people have been reported killed in a series of air strikes believed to have been carried out by Russian planes in a rebel-held city in northwestern Syria.
The strikes on December 20 were reported to have hit a busy market, several official buildings, and apartment blocks in Idlib, the capital of the province of the same name.
There were conflicting reports on casualties.
The Syrian Observatory for Human Rights said 36 people had been killed and many more injured.
But Reuters news agency quoted rescue workers as saying they had confirmed 43 dead but that at least 30 more bodies had been retrieved that had still to be identified.
Reuters added that over 150 people were wounded with some of the serious cases sent to hospitals in Turkey.
Idlib was captured earlier this year by a coalition of Islamist insurgent groups that includes the Al-Qaeda-linked Al-Nusra Front.
Russia has not confirmed whether it carried out strikes in the area.
Separately, the Syrian Army said on December 20 that it had seized -- with the backing of Russian air power -- a rebel-held town in southern Aleppo.
The capture of Khan Touman was seen as a major gain that opened the way for advances further to the west in Idlib Province.
In September, Russia began launching air strikes against armed groups in Syria, saying Islamic State militants and other "terrorists" were targets.
But the United States and its allies claim Russia's military involvement in the Syrian conflict aims at beefing up President Bashar al-Assad.
President Vladimir Putin said on December 19 that Russia’s armed forces had not utilized their full capability in Syria and would use "more military means" there if necessary.
He made the comments a day after the United Nations Security Council unanimously adopted a resolution that endorses an international road map for a peace process in Syria, where the civil war is heading into its fifth year.
The peace plan calls for a cease-fire, talks between the Syrian government and opposition in early January, a transitional government within six months, and elections under UN supervision within 18 months.
But disagreements remain between world powers over Assad's role in Syria's future.