Russia's intelligence agency said it has foiled a terror plot led by militants fighting for the Islamic State group in Syria.
The FSB said it arrested four people suspected of plotting a series of attacks, two of whom were supposed to blow themselves up on Moscow's transit system and in a shop.
The FSB said it discovered a lab outside Moscow where improvised explosive devices were made.
The intelligence agency said the attacks were directed by two senior militants who fight on the side of IS in Syria and hail from the former Soviet Union.
The suspects arrested outside Moscow were not identified, but the FSB said one of them is a Russian national and three others are from Central Asia.
The agency released a video which shows operatives inspecting a house used by the group to make explosives, while two suspects lie down on the floor in handcuffs.
It did not say when the arrests took place.
In May, the FSB arrested another group of suspected IS members who were also accused of plotting terror attacks in the capital.
The arrests follow a suicide bombing in St Petersburg's subway that left 16 dead and more than 50 wounded in April.
President Vladimir Putin said in April that some 9,000 militants, about half of them from Russia and the rest from ex-Soviet Central Asian nations, have joined IS in Syria.
He emphasised that a key goal for the Russian military operation in Syria is to crush them there and prevent them from coming back home.