The Russian military says its officers have found evidence of chemical weapons use by Syrian militants.

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said Friday that ministry experts have found unexploded ordnance and fragments of munitions containing chlorine and white phosphorus on Aleppo's southwestern outskirts. Konashenkov said the discovery proves the militants have used chemical weapons against civilians and Syrian army soldiers.

The U.S. and its allies have pushed for sanctions on the Syrian government for using chemical weapons. Russia has questioned international investigators' conclusions linking chemical weapons use to the Syrian government and pointed at evidence of their use by the militants.

The U.N. Security Council has voted to extend the mandate of inspectors working to determine those responsible for chemical weapons attacks in Syria.