Sergei Shoigu said over 2,000 militants backed by dozens of tanks and armored vehicles have launched attacks on living quarters, schools and hospitals in the government-controlled part of the city.
He also claimed the rebels blocked civilians from leaving the rebel-controlled neighborhoods, killing dozens.
The rebels in Aleppo began an offensive Friday to break the government's siege of the eastern part of the city, which has been under their control since 2012.
Shoigu said that a Russian moratorium on conducting airstrikes on Aleppo entered a 16th day today.
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Putin's spokesman, Dmitry Peskov, said that the president believes that the "humanitarian pause" should hold, but warned that the rebel offensive could trigger a change in that policy.
Peskov shrugged off a recent Times of London report alleging that Putin plans to unleash a massive aerial attack on Aleppo once the Russian aircraft carrier, the Admiral Kuznetsov, reaches Syria's shores.
The Russian Defense Ministry's spokesman, Maj. Gen. Igor Konashenkov, sought today to turn the tables on the US criticism of Russia's action in Syria by accusing the US-led coalition of striking civilians in the Iraqi city of Mosul.