The sixth straight day of bombing by Syrian regime forces on Sunday brought the death toll in eastern Aleppo to almost 300, as rescuers warn of the “heaviest bombardment” since the five-year civil war began. The Syrian regime resumed bombing Tuesday after three weeks of relative calm, destroying the city’s remaining hospitals and launching suspected chemical attacks on civilian areas. “This is the heaviest bombardment I have seen in the past five years,” Ismail Abdallah of the Syrian Civil Defense told CNN. Among the latest attacks was an onslaught on the al-Sakhour neighborhood of Aleppo, where the U.K.-based Syrian Observatory for Human rights and the Aleppo Media Center say a family of six was wiped out in a chlorine-gas attack. UN Secretary-General Ban Ki-moon has condemned the continued airstrikes, saying those responsible “must one day be brought to account” for the “war crimes.” The White House has also denounced the bombings, calling on Russia and Syria to cease their “heinous” activities.