The United States and Turkey are working together to crack down on a human smuggling network linked to the Islamic State militant movement, the U.S. Treasury Department said on Friday.

After a probe closely coordinated with Ankara, Washington imposed sanctions on four individuals, three of whom were involved in the network, it said in a statement.

"As a result of this close cooperation, (Turkey) is concurrently taking its own domestic action against this network," it said. 

The statement did not say how long the group had been operating or how many people it had smuggled.

In May, Turkish authorities said they had detained 41 people suspected of having ties to Islamic State in operations across 12 provinces. 

Islamic State controlled one third of Iraq and Syria at its 2014 peak and though beaten back, it continues to wage insurgent attacks.