"We condemn use of chemical weapons by terrorists in Syria," Salehi told German daily Der Spiegel on Sunday.
The Iranian foreign minister said that Tehran is "categorically against all weapons of mass destruction".
In March, terrorists fired a rocket containing chemical substances in the Khan al-Assal area of rural Aleppo and reports indicated that around 25 people were killed, most of them civilians. Syria immediately asked for an independent investigation into the use of chemical weapons by militants in Aleppo.
Iran called on the UN in March to adopt proper measures to prevent terrorists from using chemical weapons against the Syrian people again.
The Iranian foreign minister urged the United Nations to condemn the use of chemical weapons by the terrorists against the Syrian nation.
In a letter to the UN Secretary General Ban Ki-moon, Salehi condemned the terrorist act of the Syrian rebels in using chemical weapons against the nation, and called on the international body to adopt preventive measures to stop repetition of such accidents.
Later, Ban Ki-moon announced the decision for conducting an independent investigation into the terrorist chemical attack.
"I have decided to conduct a United Nations investigation into the possible use of chemical weapons in Syria," Ban told reporters in his office on Thursday, adding that "I intend for this investigation to start as soon as practically possible."
The chemical attack came after a video footage posted on the internet late in January showed that the armed militants in Syria possessed canisters containing chemical substances.
The foreign-sponsored militants had earlier released footage in which rabbits were killed by inhaling poisonous gas.
Iran has consistently opposed the use of weapons of mass destruction as well as chemical weapons by any country and has sent a letter to the UN Secretary-General Ban Ki-moon in this respect, he said.
We oppose any type of production, stockpiling and use of weapons of mass destruction, and this stance is the clear message and consistent policy of Iran, Salehi said.