A suspected organiser of the St Petersburg Metro suicide bombing that killed 14 passengers has been arrested while carrying a gun, authorities say.
Russia's Federal Security Service (FSB) said the suspect was arrested in Odintsovo, a city just outside Moscow.
It said the man was armed with a pistol when he was detained.
He was named by the FSB identified as Abror Azimov, 26, from ex-Soviet Central Asia.
The FSB said the man arrested on Monday is believed to have helped prepare the suicide bomber.
At least eight other people have been arrested in connection with the bombing.
The bomber in the April 3 blast was from Kyrgyzstan.
The impoverished, predominantly Muslim countries in central Asia are seen as fertile ground for Islamic extremists and thousands of their citizens are believed to have joined the Islamic State group.