LOUISVILLE, Kentucky

Turkish President Recep Tayyip Erdogan said Thursday that his Syrian counterpart, Bashar al-Assad, is a “killer” who engages in state terrorism.

“He is a killer who has murdered 600,000 of his citizens,” Erdogan told reporters at the Muhammad Ali Center in Louisville, Kentucky, where he attended a funeral prayer for boxing legend Muhammad Ali.

Assad is “in a way the occupier of a country where 12 million of its own citizens are displaced,” according to Erdogan.

“He is actually involved in state terrorism. Turkey currently houses 3 million refugees. And we are their hosts. I believe that the rest of the world should isolate Assad. And I believe the ones who are helping him are actually aiding him in his crimes,” he said in apparent reference to Russia. Moscow has been a long-time support of Assad, and last September began a campaign of airstrikes in Syria.

The international community, through the UN, is scrambling to deliver humanitarian aid to Syrian towns besieged by Syrian regime forces and its allies.

A deadline for airdrops set last month by the International Syria Support Group – working to end the crisis in the country -- recently expired without much progress in aid delivery.

The U.S. has urged the Syrian government to allow humanitarian access to besieged towns.