NATO powers and the UN chief have condemned air strikes on Syrian hospitals and schools that killed dozens of civilians on February 15, with Turkey and France saying they amounted to "war crimes" and Ankara blaming Russia for the bombings.
Kremlin spokesman Dmitry Peskov said on February 16 that Russian forces had nothing to do with the attacks and urged that "in this case, the primary source of information is the statements of official representatives of the Syrian authorities."
The United Nations said that up to 50 civilians, including children, were killed in the strikes on at least five medical facilities and two schools in the northern Syrian provinces of Aleppo and Idlib.
The bombings came as Syrian troops with Russian air support intensified an offensive on Aleppo.
UN Secretary-General Ban Ki-moon condemned the raids as "blatant violations of international law" and said they "cast a shadow" over efforts to end Syria's five-year civil war.
The United States said that two civilian hospitals were hit in and around Aleppo in northern Syria: one run by French medical group Doctors Without Borders (MSF) and another in the city of Azaz.
While the United States did not directly accuse Russia of carrying out the strikes, the State Department said such action "casts doubt on Russia's willingness and/or ability to help bring to a stop the continued brutality of the Assad regime against its own people."
Russia has been conducting air strikes in support of President Bashar-al-Assad's forces since September 30 and has backed his government's military campaign throughout the five-year war.
Moscow says it is targeting Islamic State (IS) militants and other "terrorists," but Western government say the majority of its strikes have been against more moderate opponents of Assad.
Moscow maintains that its air strikes do not target civilians, while the United States and others have accused Russia of bombing indiscriminately and causing significant civilian casualties.
Anti-Assad Syrian monitoring groups have said the Russian air campaign has been the major cause of civilian deaths in Syria since it began.
Syrian activist and journalist Baha al-Halabi told RFE/RL's Current Time on February 15 that "Russian warplanes carry out hundreds of air strikes every day."
Halabi added, "Destruction has become the general standard in Aleppo city and the outskirts. In every street, there is something that has been damaged. Every neighborhood in Aleppo has been hit by bombardment or shelling. Residential buildings are damaged. Even on the outskirts of Aleppo, every street and every area has been hit by bombardment or shelling."
The strikes on February 15 are likely to increase already mounting concerns over Russia's commitment to a cessation of hostilities starting later this week, as agreed by countries in the International Syria Support Group (ISSG) in Munich on February 12.
"That the Assad regime and its supporters would continue these attacks, without cause and without sufficient regard for international obligations to safeguard innocent lives, flies in the face of the unanimous calls by the ISSG, including in Munich, to avoid attacks on civilians," State Department spokesman John Kirby said in a statement on February 15.
French Foreign Minister Jean-Marc Ayrault said acts such as the "deliberate" bombardment of a hospital "constitute war crimes," adding that "attacks against health facilities in Syria by the regime or its supporters are unacceptable and must stop immediately."
Turkey's Foreign Ministry went a step further, blaming Russia for the attacks. Moscow has not responded to the allegations.
Kremlin spokesman Peskov said relations with Turkey were "in a deep crisis" and added that Russia "regrets this, but it is not the initiator of the crisis."
Ankara and Moscow have traded accusations and low-level sanctions since Turkey's air force shot down a Russian Su-24 military jet it claimed had ignored warnings after flying from Syria into Turkish airspace in late November.
The Syrian Observatory for Human Rights, MSF, and other authorities said the air strikes were carried out by Russian or Syrian planes.
Turkey has been hinting it may join the fight in the Aleppo region to stop Syrian Kurds from seizing strategic territory there near the Turkish border. Turkey has been shelling Kurdish troops in the area for several days.
On February 16, an unnamed Turkish official told the Reuters news agency that Ankara has asked its allies, including the United States, to consider a joint ground operation in Syria. In the past Washington has ruled out a major ground action. However, the official said Ankara "is not going to have a unilateral ground operation."
Syria's ambassador to Moscow, Riad Haddad, claimed a hospital had been hit by a U.S. air raid.
"American warplanes destroyed it. Russian warplanes had nothing to do with any of it -- the information that has been gathered will completely back that up," he told Russian state-run channel Rossia-24. He did not provide any evidence, however.
The increasing violence on the ground in Syria and war of words between NATO countries and Moscow have dampened hopes that the cessation of hostilities will take hold on schedule on February 18.
Moreover, Assad, who was not present at the Munich negotiations, said on February 15 that honoring the truce would be "difficult" and his government will continue to battle any group that has taken up arms against it, insisting all such groups are "terrorists."
"Cease-fires occur between armies and states, but never between a state and terrorists," he told members of the Bar Association in Damascus.
With reporting by Reuters, AFP, Interfax, AP, and The New York Times