"I think [the situation in Syria] is probably the most serious security threat, not only to the region but to the world at large," he said in an interview broadcast Monday by the BBC.
The Syrian Observatory for Human Rights, an opposition group which has headquarters in London, said it documented more than 120,000 casualties since the beginning of the conflict in March 18, 2011, to Oct. 30, 2013. It said that figure doesn't include the estimated 10,000 detainees and missing persons inside the country.
Iran is a close ally of Syrian President Bashar Assad and a strong supporter of Hezbollah, a Shiite militia in Lebanon fighting alongside pro-government forces in Syria.
Zarif told the BBC the Syrian conflict was taking on a sectarian tone, pitting Shiite supporters of the Assad government against their Sunni rivals. There is, however, no military solution to the conflict.
"I believe that if you want to resolve the problem in Syria, everybody has to understand that there is no military [solution]," he said.