"A commander of an American-backed rebel group said his men were not involved, and contended that other groups that had carried out attacks in the past were being brought under control. But that did not explain the civilians killed in dozens of shelling attacks on government-held neighborhoods in the past week, which suggest that American-backed groups are carrying them out, or that they are unable to stop other groups from doing so. Some anti-government activists — and even the rebel commander, who goes by the name Abu Qutaiba — suggested that the shelling of the maternity hospital had been carried out by the government to tarnish the insurgents. But other anti-government activists said they assumed the attack had been carried out by insurgents, even as they debated whether it had been a missile or rocket strike, as state media has said, or a car bomb. Some condemned the assault, like Razan Ghazawi, who wrote on Twitter that attacking medical workers was a tactic of President Bashar al-Assad and “committing those crimes only makes us a criminal like him.” Others sought to justify it. “We will target their areas more,” Khaled Eido, an activist and former fighter, said by text message, calling the attack retaliation for “the massacres the regime committed in the past and on Obama’s silence.” Abu Qutaiba, the rebel commander, said his group, called Go Straight as You Were Commanded, receives aid through a covert program run by the C.I.A. and allied intelligence agencies, including what he called “precise weapons,” and “would never randomly shell regime-held areas.” But a number of rebel groups use missiles improvised from gas canisters, which are both powerful and imprecise."