VATICAN CITY — Pope Francis says he has been disturbed by "terrible images" of atrocities occurring in Syria, and he is urging the international community to step up its efforts to end the civil war there.

Francis told tens of thousands of people in St. Peter's Square on Sunday that Syrian and rebel forces must put down their arms. He renewed his call for dialog as the US considers a military response to the alleged use of chemical weapons in Syria last week.

Francis cited the intensification of the "war among brothers," including massacres and "atrocious deeds," and he urged the international community to "put all its efforts" toward helping Syria find a solution to this "tragic situation."

He also expressed solidarity for the victims and all those suffering, especially the children.