Russia's state security service says it has arrested a group of central Asian citizens who had been ordered by leaders of "terrorist groups" in Syria and Turkey to carry out attacks in the Moscow region, Russian news agencies report.
The Federal Security Service (FSB) said the attacks had been planned for Russia's May holiday celebrations and it had seized large numbers of weapons and explosives.
"(The attacks) were ordered by leaders of international terrorist groups operating in Syria and Turkey," Interfax news agency quoted the FSB as saying on Wednesday (local time).
Russian security services are on high alert for attacks by extremist groups in Moscow and other major Russian cities.
Russian forces are helping the Syrian government to fight Islamic State and other opposition groups in Syria. Islamic State has claimed responsibility for several attacks in Russia, mostly in the Caucasus region.
The FSB arrested around 20 Islamic State followers in March who it said were trying to recruit new fighters in Russia.