DW quoted an Iraqi military commander as saying the women were discovered in a series of underground tunnels built by Islamic State to move throughout the city undetected.

They were reportedly wearing explosive belts when they were arrested.

By mid-2015, 4,700 jihadists from Russia and Central Asia had traveled to Iraq and Syria to join Islamic State, according to the New York-based Soufan Group (TSG). The security think-tank estimated that the flow of fighters from Russia and the former Soviet Union had increased threefold from June 2014.

In May 2016, Russian security services arrested a 21-year-old student from the Moscow State University, Varvara Karaulova, for attempting to join the radical organization. She was sentenced to more than four years in prison in December 2016.

*Islamic State is banned in Russia as a terrorist organization.