Rebels in the Free Syrian Army have denied government claims that they have fired chemical weapons at a village.
Calling it the "first act" by an interim government, information minister Omran al-Zoubi said the missile, loaded with "poisonous gases", was fired at Khan al-Assal village in Aleppo province, killing 16 and wounding 86. Zoubi said Turkey and Qatar, which have supported rebels in their efforts to topple president Bashar al-Assad, had "legal, moral and political responsibility" for the attack.
Syria's main opposition coalition is holding talks to form an interim government to provide basic services for areas freed from Assad's iron fist.
"Terrorists launched a missile containing chemical products into the region of Khan al-Assal," Sana news agency said.
But a Syrian rebel commander denied state media reports, saying that the government had fired the rocket.
"We were hearing reports about a regime attack on Khan al-Assal, and we believe they fired a Scud with chemical agents. Then suddenly we learned that the regime was turning these reports against us," said Qassim Saadeddine, a senior rebel and spokesman for the Higher Military Council in Aleppo.
"The rebels were not behind this attack."
The Aleppo media centre, affiliated with the rebels, confirmed there had been cases of "suffocation and poison" among civilians in the Khan al-Assal area but blamed pro-Assad forces for the use of "poisonous gases".
The Syrian government has a large stockpile of chemical weapons.