At a preliminary court hearing Monday to formalize the arrest, Abror Azimov confessed to indirectly participating in the preparation of the attack on the St Petersburg metro, which claimed 14 lives, but denied organizing it.

"I do not oppose being arrested. But I did not say that I was involved in the blast," Russian news agencies quoted Azimov as saying.

"There was some involvement by me, but not direct. I was given an order. I did not understand that I was taking part in terrorist activity."

The court later ordered 27-year-old Azimov to be held in detention until June 3, as investigations continue.

Ongoing investigation

Russia's FSB security service had reportedly detained Azimov one day earlier in the Odintsovo suburb of Moscow. The FSB added the suspect was then questioned by the Investigative Committee, which is in charge of probing serious crimes.

Authorities identified the suspected suicide bomber as 22-year-old Akbarjon Djalilov earlier this month. Djalilov is believed to have been a Russian national born in Central Asian Kyrgyzstan.

Eight suspects were previously detained over the bombing. The head of the FSB Alexander Bortnikov said last week that they had all come from Central Asia.

No one has claimed responsibility for the attack. Investigators are probing possible ties to so-called "Islamic State" (IS) jihadists, who have threatened to attack Russia in revenge for its military intervention in Syria.

ss/msh (AFP, Reuters)