Speaking on condition of anonymity for security reasons, he said around 24 people were killed and many others wounded, with many of them in critical condition.
Syrian regime aircraft Friday carried out at least 25 strikes on Palmyra, killing eight civilians and 12 Islamic militants in the ancient city held by the Islamic State in Iraq and Syria (ISIS) group, a monitor said.
The Syrian Observatory for Human Rights said it was one of the most sustained government bombardments on Palmyra. Such discrepancies are common in the aftermath of large bombings. They reported casualties but had no specific figures. The region is often targeted by a U.S.-led coalition fighting IS from the air. Syrian government attacks typically concentrate on rebel-held areas of the country.
According to the Observatory, 17 people were killed Friday in government air raids on the city of Idlib, stronghold of the Army of Conquest, an alliance of Islamist and militant groups.
Mr Kerry said: “Our focus remains on destroying ISIL [ISIS militants] and also on a political settlement with respect to Syria, which we believe can not be achieved with the long-term presence of Assad“.
The airstrikes occurred as the United Nations envoy to Syria, Staffan de Mistura, was in Damascus.
De Mistura held a meeting with Syrian Foreign Minister Walid al-Moallem, during which the latter emphasized that fighting terrorism has been a priority for the Assad regime.