"We do not want foreign intervention in Syria but we do not accept and will not accept any operations against civilians," Davutoğlu told Turkish business people at a dinner.
Davutoğlu urged Assad on Monday to end military operations against civilians immediately and unconditionally, saying this was Ankara's "final word.
Turkish leaders, who once backed Assad, are sounding increasingly frustrated at the Syrian leader's fierce crackdown on demonstrators demanding an end to his 11 years in power.