George Ourfalian / Reuters
Residents and medics transport a wounded Syrian army soldier to hospital Tuesday after heavy fighting in Aleppo province during which both rebels and government forces said a chemical weapon was used.
By Ian Johnston and Ammar Cheikomar, NBC News
A chemical weapon was used during fierce fighting in a strategically important Syrian town, rebels and the government claimed Tuesday, with each side blaming the other for the deadly attack.
If it is confirmed that a banned chemical agent was used, it could significantly change the international response to the ongoing civil war.
The death toll was put at 25 by Syria?s state-run SANA news agency, which said dozens of other people were injured.
White House spokesman Jay Carney addresses reports that chemical weapons may have been used in Syria as civil war continues under the rule of President Bashar Assad.
A photographer for the Reuters news agency visited hospitals in the city of Aleppo, and said a number of patients had breathing difficulties. They told him of people dying and ?suffocating in the streets.?
SANA blamed the rebels for the attack, which happened in Khan al-Asal in Aleppo province.
?Terrorists on Tuesday launched a rocket containing chemical materials,? it said.
?Initial information indicated that about 16 citizens were killed, and 86 others were injured, most of them are in critical condition. Later, the death toll due to the firing of the rocket rose up to 25 martyrs,? it added.
SANA?s website showed photographs of a number of people, including several children, in what appeared to be a hospital.
'Convulsions, then death'
Information Minister Omran al-Zoabi said that ?the substance in the rocket causes unconsciousness, then convulsions, then death,? Reuters reported.
Rebel spokesman Fahd al Masry said there was ?a state of panic and fear among the civilians and dozens of cases of suffocating and poisoning? after what he said was a Scud missile attack by the government -- "most probably usage of chemical weapons."
"This is not the first time," he added.
George Ourfalian / Reuters
A man is treated at a hospital after a chemical weapons attack in Syria's Aleppo province. Rebels and Syrian government forces blamed each other for the attack.
Masry blamed not only the Assad regime but foreign governments that have not gotten involved in the war. "They?wouldn't?have used it if not for the silence of the international community on the crimes and massacres committed in Syria for the past two years," he said, adding that the rebel forces may "be forced to reevaluate the rules of engagement in the coming days."
Khan al-Asal is the last town in the area to the west of Aleppo that has not been taken by the rebels, and if it fell that would hamper the flow of supplies to the regime?s forces in the city.
The town's population has traditionally been split between Sunni Muslims, who tend to be sympathetic toward the rebels, and Shiites, who are more likely to be pro-Assad.
White House spokesman Jay Carney said Tuesday the U.S. was looking carefully at allegations that both sides are using chemical weapons, but he said he was skeptical of any claims made by the Syrian regime, The Associated Press reported.
He added there was no evidence to back up the Assad regime's claim that Syrian rebels have used chemical weapons.
Carney said it was a serious concern for the U.S. that the Assad regime could use such weapons, the AP reported. He said President Barack Obama believed that would be unacceptable and that there would be consequences.?
The Organization for the Prohibition of Chemical Weapons (OPCW) also said it was aware of the reports and hoped to release a statement later Tuesday.
A look back at the conflict that has overtaken the country.
On Dec. 24 last year, there were claims that a number of Syrians were killed after inhaling ?poisonous gases? released by government forces in rebel-held areas of the city of Homs.
OPCW spokesman Michael Louhan said the body was asked by the United Nations to give its assessment of this incident, but it was unable to find any ?conclusive information regarding whether they were banned chemical weapon substances or not.?
According to the international body, the Chemical Weapons Convention says it was created ?for the sake of all mankind, to exclude completely the possibility? of their use.
The U.K., which recently announced it was sending armored vehicles to the rebel forces, warned Tuesday that if the use of chemical weapons was confirmed it would change its approach.
?We are aware of today?s press reports alleging that a chemical weapon was fired in the north of Syria and we are looking into this,? a spokesman for the U.K. Foreign Office said.
?The use of chemical weapons would be abhorrent and would be universally condemned,? he added. ?The U.K. is clear that the use or proliferation of chemical weapons would demand a serious response from the international community and force us to revisit our approach so far.?
Russia ? one of Syria?s dwindling number of allies - blamed the opposition, saying it was ?seriously concerned? that ?weapons of mass destruction are falling into the hands of the rebels,? according to a foreign ministry statement reported by Reuters.
People resisting the army of President Bashar al-Assad in northern Syria cope with loss and prepare for fighting.
The Reuters photographer said victims he had visited in Aleppo hospitals were "mostly women and children."
"They said that people were suffocating in the streets and the air smelt strongly of chlorine,"?said the photographer, who Reuters said cannot be named for his own safety.?
The photographer quoted victims he met at the University of Aleppo hospital and the al-Rajaa hospital as saying: "People were dying in the streets and in their houses."
Reuters described footage aired by Syrian state television:
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, but some interviewed said they had trouble breathing.
An unidentified doctor interviewed on the channel said the attack was either "phosphorus or poison" but did not elaborate.
"The Free Syrian Army hit us with a rocket, we smelled something and then everyone got dizzy and fell down. People were falling to the ground, " said a sobbing woman, lying on a stretcher with a drip in her arm.
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 man in a green surgical mask, who said he had been helping to evacuate the casualties, said: "It was like a powder, and anyone who breathed it in fell to the ground."
Reuters and The Associated Press contributed to this report.
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This story was originally published on Tue Mar 19, 2013 8:10 AM EDT