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NEW: "Hundreds of critical medical evacuations are urgently required," a U.N. official says

Activists report dozens more deaths across the besieged Syrian city

CNN  — 

Russia warned the United States about taking direct action against the Syrian regime, saying it would cause negative consequences across the Middle East, Russia’s state-run Sputnik news agency reported Saturday.

Meanwhile, intense fighting continued in the besieged Syrian city Aleppo on Saturday, with one of the main hospitals bombed by Russian-backed Syrian forces.

Sputnik reported that Russian’s Foreign Ministry spokeswoman Maria Zakharova said, “If the US launches a direct aggression against Damascus and the Syrian army, it will lead to terrible, tectonic shifts not only on the territory of this country but also in the region in general.”

She said the United States risked creating a power vacuum in Syria were it to depose Syrian President Bashar al-Assad. Such a power vacuum would be filled by “terrorists of all sorts,” Sputnik reported.

Secretary of State John Kerry, in a meeting with a group of Syrian civilians last week, expressed sympathy for their demands that the United States intervene more forcefully amid Syrian a