Whether the weapons actually were used could not be immediately confirmed.  The Syrian rebel forces are not known to possess chemical weapons, while the government has large stockpiles. There has long been a fear on all sides — in the Syrian government, in neighboring Israel and among the rebels’ western backers — that rebel groups could seize chemical weapons, but it is unclear whether any such weapons have been loaded onto rockets or missiles for use, or whether the rebels would be able to fire them if they were.  The Syrian state news agency, SANA, said “terrorists” fired a rocket “containing chemical materials” into the Khan al-Assal area of Aleppo, and a government official told state television that the episode would be reported to human rights organizations and to countries supporting the rebels.  But a senior rebel commander, Qassim Saadeddine, who is also a spokesman for the Higher Military Council in Aleppo, blamed Assad’s forces for any chemical strike. “We were hearing reports from early this morning about a regime attack on Khan al-Assal, and we believe they fired a Scud with chemical agents,” he told Reuters by telephone from Aleppo.  The Syrian Observatory for Human Rights, a Britain-based watchdog group, said witnesses heard over walkie-talkies that 26 people were killed, including 16 government soldiers and 10 civilians, after a rocket landed on Khan al-Assal. Activists said the government tried to hit the police academy there, which was recently taken by rebel forces, with a Scud missile, but it accidentally fell on a government-controlled area instead.  President Obama has said that a chemical attack would cross a “red line” that could prompt military intervention by the United States. Israel has said it would intervene to stop chemical weapons from slipping out of the Syrian government’s control and into the hands of either the rebels or Hezbollah, the Lebanese militant group allied with the Syrian government.  In Washington, the White House cast doubt on claims that the opposition had used chemical weapons, and said it was evaluating the possibility that the government had used them.  “We’re looking carefully at allegations of C.W. use, chemical weapons use,” said Jay Carney, the White House press secretary. “The use of chemical weapons would be totally unacceptable.” If Mr. Assad’s government has used such weapons, he added, “there would be consequences, and they would be held accountable.” Mr. Carney would not say specifically what the consequences would be.  He said the administration was “deeply skeptical” of the assertions by the government of President Bashar al-Assad that the opposition had mounted a chemical attack. “We have no evidence to substantiate the charge that the opposition has used chemical weapons,” he said. He warned Mr. Assad against using such claims as a “pretext or cover” to justify his own use of them.  Mahmoud Moussa, an anti-government activist, said on Tuesday that activists reported government use of chemical weapons not only in Khan al-Assal in Aleppo but also in Al Atebah in the eastern countryside near Damascus. None of the reports could be confirmed.  Rebel factions have accused the government of using chemical weapons many times, but there have as yet been no confirmed cases. The term “chemical weapons” has sometimes appeared to be used loosely to include not just deadly nerve agents like sarin gas but also tear gas and other nonlethal irritants used for crowd control.  The Syrian information minister, Omran al-Zoabi, was quoted by state television saying that Turkey and Qatar, which have backed the rebels in the conflict, bore “legal, moral and political responsibility” for what he called the chemical weapons attack, Reuters reported. A Turkish government official called the claim baseless, the news agency said.  Last week, Maj. Gen. Aviv Kochavi, Israel’s head of military intelligence, warned that the Syrian president, Bashar al-Assad, was “making advance preparations to use chemical weapons.”  General Kochavi, speaking at a security conference in Israel, said Mr. Assad “did not give the order yet, but is preparing for it.”  An Israeli military official said on Tuesday said the country was closely monitoring the situation in Syria.  Likewise, the director-general of an international anti-chemical weapons organization said it was monitoring events in Syria. “I don’t think we know more than you do at the moment,” the director-general, Ahmet Üzümcü, was quoted by Reuters as telling the audience at a seminar in Vienna.  SANA published photographs of what it said were civilian victims of the attack. The photos showed men, women and children on hospital beds or stretchers, some of them hooked up to drips or under the care of medics. Several of the patients had what appeared to be devices to help them breathe.  The report said that “terrorists” fired a missile containing chemical materials into Khan al-Assal, killing 25 people and wounding 86, most of them seriously.  A Reuters photographer was quoted in a report by the news agency as saying that he had visited victims in Aleppo hospitals, and that they were suffering breathing problems.  “I saw mostly women and children,” said the photographer, who Reuters said it could not identify by name out of concern for his safety.“They said that people were suffocating in the streets and the air smelt strongly of chlorine.”  The photographer said victims he met at the University of Aleppo hospital and the al-Rajaa hospital told him that “people were dying in the streets and in their houses.”  Isabel Kershner contributed reporting from Ramallah, West Bank, and Peter Baker from Washington.
The Syrian government says rebels fired chemical weapons in Aleppo; activists say it was the government. Neither account has been confirmed.