KABUL - Former Afghan president Hamid Karzai accused his successor on Saturday of committing treason by allowing the US military to drop the largest conventional bomb ever used in combat during an operation against Islamic State militants in Afghanistan.Karzai, who also vowed to "stand against America," retains considerable influence within Afghanistan's majority Pashtun ethnic group, to which President Ashraf Ghani also belongs. His strong words could signal a broader political backlash that may endanger the US military mission in Afghanistan.Afghan defense officials have said the 21,600-pound (9,797-kg) GBU-43, dropped late on Thursday in the eastern province of Nangarhar, had killed nearly 100 suspected militants, though they acknowledged this was an estimate and not based on an actual body count."How could you permit Americans to bomb your country with a device equal to an atom bomb?" Karzai said at a public event in Kabul, questioning Ghani's decision. "If the government has permitted them to do this, that was wrong and it has committed a national treason."Ghani's office said the strike had been closely coordinated between Afghan and US forces and replied to Karzai's charges with a statement saying: "Every Afghan has the right to speak their mind. This is a country of free speech."Public reaction to Thursday's strike has been mixed, with some residents near the blast praising Afghan and US troops for pushing back the Islamic State militants.While the bomb has been described as one of the largest non-nuclear devices ever used, its destructive power, equivalent to 11 tonnes of TNT, pales in comparison with the relatively small atomic bombs dropped on Japan in 1945, which had blasts equivalent to between 15,000 and 20,000 tonnes of TNT.