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.