Russia's federal security service 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" during raids on Thursday, the FSB security service said in a statement.
"The militants were preparing the terrorist attacks on direct orders of a Turkey-based emissary of the Islamic State international terrorist organisation, who has been put on an international wanted list by Tajikistan," the statement said.
The FSB did not identify the suspect in question but said the four people detained were citizens of Tajikistan and Moldova.
The group was "planning to carry out a series of high-profile terrorist attacks in Moscow using powerful homemade explosive devices."
An AFP employee at the scene of the FSB operation in southern Moscow saw a block of apartments cordoned off for several hours as special forces stood by.
During the raid, police seized firearms and ammunition as well as "homemade explosive devices and a large amount of explosive blend material for making a high-energy explosive device."
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.
Moscow launched a bombing campaign in Syria last year in what it claimed was an attempt to prevent terror attacks in Russia.
The Russian defence ministry told local media Thursday that more than 2,000 jihadists from Russia and other former Soviet republics were killed in Syria last year.