Syria's government on Tuesday accused rebel forces of using chemical weapons in the Aleppo province, while opposition activists said the regime used chemical weapons outside Damascus.
"Terrorists fired rockets containing chemical materials on Khan al-Assal in Aleppo province, and preliminary information suggests 15 people were killed, mostly civilians," the state news agency SANA and Syrian state television said.
However, Free Syrian Army spokesperson Louay Almokdad said the regime was behind the attack.
"We understand the army targeted Khan al-Assal [in Aleppo province] using a long-range missile, and our initial information says it may have contained chemical weapons," he said.
"There are many casualties and many injured have breathing problems."
"We have neither long-range missiles nor chemical weapons. And if we did, we wouldn't use them against a rebel target," Almokdad added.
Syrian Information Minister Omran al-Zoubi commented on the incident, saying that “launching rockets with chemical weapons is a grave escalation.”
He also accused Turkey and Qatar of standing behind the attack
“Turkey and Qatar are responsible for the chemical attack.”
A Reuters photographer said that victims of the attack were receiving treatment in hospitals in regime controlled areas, which he visitied.
"I saw mostly women and children," he said. "They said that people were suffocating in the streets and the air smelt strongly of chlorine."
"People were dying in the streets and in their houses," Reuters quoted the photographer as saying.
Meanwhile, the opposition Syrian Local Coordination Committees said that a regime chemical weapon attack on the town of Atiba outside Damascus killed three people and wounded several others.
A video uploaded on Tuesday showed victims struggling to breathe purportedly following the attack in the Damascus province.
The regime's accusation is its first such against rebel forces, though the international community has warned the regime against deploying its own stocks of chemical weapons.
There are also concerns that the weapons could fall into the hands of militants, with the United States and Israel particularly concerned about the fate of the arms if the regime loses control over them.
Syria's chemical weapons stockpile, which dates back to the 1970s, is the biggest in the Middle East, but its precise scope remains unclear, according to analysts, and the regime has not acknowledged having the arms.
The country has hundreds of tons of various chemical agents, including sarin and VX nerve agents, as well as older blistering agents such as mustard gas, dispersed in dozens of manufacturing and storage sites, experts say.
But it remains unclear if the chemical weapons are mounted and ready to be launched on Scud missiles, if the chemical agents are maintained effectively, and whether the regime is able to replenish its chemical stocks.
Damascus has said it might use its chemical weapons if attacked by outsiders, although not against its own people.