Russia media outlets repot that Russia’s Federal Security Service (FSB) said Thursday it had thwarted a series of attacks by Islamic State militants in Moscow and the southern city of Samara, detaining six people.

Four members of the terrorist group were detained in Moscow on Thursday, the FSB security service said in a statement.

The FSB said the detainees are citizens of Moldova and Tajikistan, noting that they were planning “a series of high-profile terrorist attacks in Moscow with the use of powerful improvised explosive devices.”

It said they were acting on “direct instructions” from a member of the extremist group Islamic State (IS) who is based in Turkey and is wanted in Tajikistan for unspecified crimes.”

In a separate statement, the FSB said it had arrested two further suspects in Samara.

TNT was allegedly found at the homes of the men who are from Central Asia and born in 1992 and 1995.

The FSB did not say if the arrests were linked to those in Moscow.

The Russian defense ministry told local media on Thursday that more than 2,000 jihadists from Russia and other former Soviet republics were killed in Syria last year.