A Russian police officer speaks to the media in the building where homemade explosives were found for terrorist activities in Moscow. (Source: AP)

On October 12, the Russian Federal Security Service (FSB) said that the Russian citizens who were recently arrested on charges of plotting a terrorist attack in Moscow had undergone training at Islamic State (IS) militant camps in Syria.

According to the latest announcement from the FSB, these subjects returned and "lay low" long before Russian President Vladimir Putin ordered airstrikes on IS targets in Syria at the request of the government of this Middle Eastern country.

Previously, on October 11, the Russian National Anti-Terrorism Committee (NAK) said that on the same day it had arrested a group of people who were preparing to carry out a terrorist attack on the public transport system in the capital Moscow.

In the room where the suspects were hiding, Russian authorities discovered and seized many bomb-making materials and up to 5kg of explosives.

Meanwhile, according to Russia's Interfax news agency, the plotters of the terrorist attack were arrested at a house on Strelbischensky Street in the western part of Moscow.

Russian authorities are continuing to investigate the incident./.

According to Vietnam+