Russian President Vladimir Putin says it's impossible to defeat the Islamic State group without cooperating with the Syrian government.

Speaking Tuesday at a meeting of a Moscow-dominated security alliance of ex-Soviet nations in Tajikistan, Putin said that Moscow has provided military assistance to President Bashar Assad's government and will continue to do so.

He shrugged off allegations that Moscow's support for Assad has sparked a flow of refugees, saying in a televised statement that without Russia's support for Assad's regime the number of Syrian refugees heading to Europe would have even bigger.

The U.S. says that Russia is in the midst of a steady military buildup at a Syrian airport, indicating Moscow intends to create an air operations base there, although no fighter jets or helicopters have arrived yet.