BEIRUT: Hours after the alleged use of chemical weapons in Syria Tuesday, it remained unclear whether any such attack had occurred, though both the government and the rebels traded blame over the reported incident.

The Obama administration dismissed a claim by Syrian President Bashar Assad’s government that the U.S.-backed rebels used chemical weapons, calling it a desperate attempt by a beleaguered regime to distract attention from its own ledger of atrocities after two years of civil war. A U.S. official went further and said there was no evidence either side had used such weapons in an attack in northern Syria, disputing a competing claim by rebels that it was regime forces who fired the chemical weapon. Spokespeople for the White House and the State Department rejected only the Assad regime’s charge.

The origin of the attack is still unclear, the official added. But the official noted that the Organization for the Prohibition of Chemical Weapons also was reporting no independent information of chemical weapons use. The official spoke on condition of anonymity.

“We have no reason to believe that these allegations represent anything more than the regime’s continued attempts to discredit the legitimate opposition and distract from its own atrocities committed against the Syrian people,” State Department spokeswoman Victoria Nuland told reporters.

“We don’t have any evidence to substantiate the regime’s charge that the opposition even has CW [chemical weapons] capability,” she added. U.N. chief Ban Ki-moon and the head of the OPCW said they were deeply concerned about the alleged attack.

“The secretary-general remains convinced that the use of chemical weapons by any party under any circumstances would constitute an outrageous crime,” Ban’s office said in a statement after he spoke by telephone with OPCW Director General Ahmet Uzumcu. Syria’s state-run news agency said 25 people were killed in the attack on the Khan al-Asal village in northern Aleppo province. It said 86 people were wounded, some in critical condition.

State TV aired footage of what it said were casualties arriving at a hospital in Aleppo. Men, women and children were rushed inside on stretchers as doctors inserted medical drips into their arms and oxygen tubes into their mouths. None had visible wounds to their bodies.

An unidentified doctor interviewed on the channel said the attack was either “phosphorus or poison” but did not elaborate.

A young girl on a stretcher wept as she said: “My chest closed up. I couldn’t talk. I couldn’t breathe. ... We saw people falling dead to the floor. My father fell, he fell and now we don’t know where he is. God curse them, I hope they die.”

A Reuters photographer said victims he had visited in Aleppo hospitals were suffering from breathing problems and that people had said they could smell chlorine after the attack.

He quoted victims at the University of Aleppo hospital and the Al-Rajaa hospital as saying people were dying in the streets and in their houses.

One of the international community’s top concerns since fighting began is that Syria’s vast arsenal of chemical weapons could be used by one side or the other or could fall into the hands of foreign jihadist fighters among the rebels or Hezbollah, which is allied with the regime.

The accusations emerged only a few hours after the opposition elected Ghassan Hitto as premier to head an interim government that would rule areas seized by rebel forces from the regime. Information Minister Omran al-Zoubi called it the “first act” of the newly announced opposition interim government.

Rebels quickly denied the report and accused regime forces of firing the chemical weapon.

The regime has not said that rebels have been able to seize any chemical weapons “so we assume that the opposition does not possess such weapons,” said Mustafa Alani, an analyst with the Gulf Research center in Geneva.

“I would not rule out that the military would use chemical weapons and try to pin it on the rebels,” Alani said.

“The only strategy that this regime has been left with is character assassination of the opposition and blame the rebels for all the bad things that are happening in the country.” Syria’s policy has been not to confirm or deny if it has chemical weapons. But in July, then-Foreign Ministry spokesman Jihad Makdissi said Syria would only use chemical or biological weapons in case of foreign attack, not against its own people.

The ministry then tried to blur the issue, saying it had never acknowledged having such weapons. But the regime is believed to possess nerve agents and mustard gas. It also possesses Scud missiles capable of delivering them, and activists said Tuesday’s attack was with a Scud missile. Russia backed the regime’s assertion.

The Russian Foreign Ministry said the rebel use of chemical weapons represented an “extremely dangerous” development in a conflict that has already killed 70,000 people. It said the rebels detonated a munition containing an unidentified chemical agent, but didn’t give further details.

White House spokesman Jay Carney said the U.S. was looking carefully at all allegations, but said the Obama administration is “deeply skeptical” of any claims emanating from Assad’s regime. He said President Barack Obama believes any chemical weapons use would be unacceptable.

“This is an issue that has been made very clear by the president to be of great concern to us,” Carney said, adding that if the Syrian regime does use such weapons, “there will be consequences.”