Russia says it has information proving that militants fighting against the Syrian government used chemical weapons in the northern city of Aleppo.

According to Syria’s official news agency SANA, at least 25 people were killed and many others injured after militants fired missiles containing "poisonous gases" into Aleppo’s Khan al-Assal village on Tuesday. Women and children are reported to be among the victims.

"A case of the use of chemical weapons by the armed opposition was recorded early in the morning of March 19 in Aleppo province," the Russian foreign ministry said in a statement shortly after the attack.

"We are very seriously concerned by the fact that weapons of mass destruction are falling into the hands of the rebels, which further worsens the situation in Syria and elevates the confrontation in the country to a new level," the statement added.

Syria's Information Minister Omran al-Zoubi described militants’ use of chemical weapons as the "first act" by the so-called opposition interim government.

He also said that Turkey and Qatar, which support militants fighting against the government of President Bashar al-Assad, bore "legal, moral and political responsibility" for the chemical attack in the northern city of Aleppo.

Foreign-backed militants, who had threatened to use chemical weapons against the army government forces and Assad supporters a few months ago, have denied using chemical weapons and have accused government forces of being behind the attack.

The attack comes hours after Syria's opposition National Coalition elected Ghassan Hitto, a former US-based IT executive, as prime minister for what it called an interim government.