(CNN) -- At least 25 people were killed Tuesday when a rocket struck a bus in Syria's commercial capital of Aleppo, the opposition Aleppo Media Center said.
The strike from the government controlled Al-Nayrab military airbase burned all those inside the bus beyond recognition, the center said.
Children, women and men were on board, and the wreckage made it impossible to know immediately "the final death toll of the massacre," the group said in a prepared statement.
A two-week offensive on Aleppo by the Syrian military had killed 517 people before this attack, the opposition Syrian Observatory for Human Rights said. Opposition groups blame the regime's use of barrel bombs -- oil drums packed with TNT and shrapnel -- for many of the deaths.
Syrian state-run media, meanwhile, said the speaker of the People's Assembly, Mohammad Jihad al-Laham, told the assembly "that the terrorist war hatched against Syria has failed, and despite all the destruction, murder and abduction committed by terrorism, the Syrian people continue to live their lives and the state's establishments continue to carry out their duties."