France's president says a "body of evidence" suggests that chemical weapons were used during attacks on a Damascus suburb that killed hundreds, and that Syrian President Bashar Assad's regime was most likely behind it.

According to a statement Sunday from his office, Francois Hollande said "everything" leads France to believe the regime was behind the attack. It didn't elaborate.

International aid group Doctors Without Borders said Saturday it had tallied 355 deaths from Wednesday's attack in Damascus' eastern Ghouta suburb.

Assad's regime and Syria's rebels have traded accusations about who was behind it.

The question has fanned debate about possible military intervention in this Middle Eastern country mired in civil war since 2011.

U.S. naval forces have moved closer to Syria as President Barack Obama considers a military response.