Almost two years since Islamic State militants started taking territory to form their so-called caliphate, residents of a Syrian town are showing how people are now fighting back.

At least 15 extremists have been killed in a dozen separate attacks in Mayadeen, on the Euphrates River, since the beginning of the year. Some have died in clashes with gunmen at or near Islamic State positions, said Rami Abdurrahman, head of a group that documents Syria's war through a network of activists.

While Syrians "had fear" under President Bashar Assad, Islamic State "is a whole different degree of tyranny," said Joshua Landis, director of the Center for Middle East Studies at the University of Oklahoma and an expert on Syria. "The idea of Islamic State, it's like communism: You want everybody to behave in a certain way, but you can't."