A man suspected of linked in Wednesday’s supermarket bombing in the Russian city of St. Petersburg was arrested, announced the country’s main domestic security agency.
Eighteen people were wounded when a device exploded Wednesday in a storage area for customers' bags. Investigators said the homemade device contained 200 grams (7 ounces) of explosives and was rigged with shrapnel to cause more damage.
Eight people remain hospitalized.
The Federal Security Service, or FSB, did not identify the suspect or provide any details about his motive. The agency said in a statement carried by Russian news agencies that he organized and carried out the attack on his own.
The ISIS terrorist group claimed responsibility for the blast, but a member of the security committee in the lower house of Russia's parliament cast doubt on the claim, saying it might have been an attempt by ISIS to gain publicity.
"Now, when the ISIS defeat in Syria seriously dented its image, it will try to restore its authority and claim responsibility for the attacks by others," Adalbi Shakhgoshev said, according to Russian news wires.
The FSB said that it has handed over the suspect to the Investigative Committee, the nation's top investigative agency. The FSB normally deals with terror suspects itself, and the transfer could indicate that the man had other motives.
The Interfax news agency reported that the suspect was a 35-year old local resident who said he was a member of an occult movement and was taking drugs.
Russian law enforcement agencies stopped short of immediately describing the supermarket blast as a terror attack, but President Vladimir Putin called it one Thursday. He added that he ordered security agencies to kill terror suspects on the spot if they resist arrest.
In April, a suicide bombing in St. Petersburg's subway left 16 people dead and wounded more than 50. Russian authorities identified the bomber as a 22-year old Kyrgyz-born Russian national.
Earlier this month, Putin telephoned US President Donald Trump to thank him for what the Kremlin described as a CIA tip that prevented more bombings in St. Petersburg, Putin's hometown.
The Federal Security Service said seven IS-linked suspects were arrested in connection to the alleged plot. The Kremlin said the suspects had planned to bomb the landmark Kazan Cathedral and other crowded sites.