An explosive device has been made safe in a flat in St Petersburg by Russian police, three days after a bomb on the city’s metro left 14 people dead.
A city official said several suspects were detained after police raided the flat early on Thursday morning, Ria Novosti reported.
Neighbours were moved away and witnesses said three men were led out in handcuffs, the agency said.
The main suspect in the metro bombing, Akbarzhon Jalilov, died in the attack.
Aged 22 and from the Central Asian republic of Kyrgyzstan, his remains were identified by his parents on Wednesday.
The flat raided at around 05:00 local time (01:00 GMT) on Thursday was in Tovarichesky Prospekt in the east of St Petersburg.
Sources told Interfax news agency that investigators were examining possible links between the three men and the alleged bomber. Jalilov himself had been renting a flat in the north of Russia’s second city.
Russia’s Investigative Committee made no reference to the arrests but said on Thursday they had established that “several citizens of Central Asian republics were in contact with Jalilov”.
While searching the flat they had been living in, investigators said they had found “items of significance for the investigation”.