Russia’s main security agency says it has arrested a man suspected of setting off an explosion at a supermarket in the Russian city of St. Petersburg that injured more then 10 people on December 27.
The Federal Security Service, or FSB, made the announcement in a December 30 statement carried by Russian news agencies.
The agency did not identify the suspect or provide any details about his motive.
The statement said the suspect organized and carried out the attack on his own.
The extremist group Islamic State (IS) had earlier claimed responsibility for the bombing.
The claim was made by the IS's Amaq news agency on December 29.
It offered no evidence for its claim. The IS often claims responsibility for terrorist attacks worldwide that are carried out by people inspired by the extremist group but often with no formal ties to it.
Russian President Vladimir Putin said one day after the blast that the explosion was a terrorist act, and urged security forces to "take no prisoners" when dealing with imminent threats from terror-plot suspects.
Investigative Committee spokeswoman Svetlana Petrenko said on December 27 that the "homemade bomb" that ripped through a customer locker area at a Perekryostok supermarket exploded with the power equivalent to 200 grams of TNT.
But law enforcement authorities initially opened an investigation on suspicion of attempted murder, seeming to suggest that terrorist motives were not suspected.