An unexploded bomb has been found in St Petersburg during police raids searching for accomplices in a terror attack that killed 14 people.

Russian security services said the explosive device found in a residential building was similar to one discovered on the city’s metro days before.

Hidden in a bag and apparently disguised as a fire extinguisher, that bomb had been covered in metal pellets designed to cause maximum destruction at Ploshchad Vosstaniya station.

The latest device was found inside a flat raided in the early hours of Thursday morning in the city’s Tovarichesky Prospekt district.

Disposal experts defused it after evacuating people living in flats on two stairwells in the nine-storey block.

“We were told: the house is mined, get out quickly,” one woman, who only gave her name as Tatiana and lives in the building, told Reuters.

Another resident, who gave his name only as Anatoly, said he had seen police detain four young men occupying an eighth floor flat next door.

“An explosive device found in the flat has been made safe,” local administration head Konstantin Serov said.

“Several suspects have been arrested; they didn’t resist and there’s now no threat to local people.”

Explosion at St Petersburg metro station

Sources told Interfax news agency that investigators were examining possible links between detained men and the alleged bomber.

The first unexploded bomb was found on Monday near the bottom of metro escalators, with local reports saying it contained 1kg of explosives packed inside a metal cylinder, covered in ball bearings.

Minutes after the discovery, an explosion ripped through a train travelling between Sennaya Ploshchad and Tekhnologichesky Institut station, killing 14 people and injuring 50 more.

The suspected bomber was among those killed, with authorities identifying him as 22-year-old Akbarzhon Jalilov, a Kyrgyz-born Russian citizen.

The attack has put renewed focus on the large number of migrants from mostly Muslim central Asian states who have moved to Russia to work.

St. Petersburg metro blast Show all 5 1 /5 St. Petersburg metro blast St. Petersburg metro blast An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Emergency services work outside Sennaya Square metro station in St Petersburg Reuters St. Petersburg metro blast An injured person is helped by emergency services outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Emergency services direct pedestrians outside Sennaya Ploshchad metro station, following explosions in two train carriages at metro stations in St. Petersburg Reuters St. Petersburg metro blast Twitter/ varlamov

Russia’s investigative committee, which is charged with the terror investigation, said it was looking into the backgrounds of suspected accomplices.

It said it had identified several people of central Asian origin who had been in touch with Jalilov and uncovered important evidence in searches of their homes.

It was unclear if those detained at the site of Thursday’s bomb scare were the suspected accomplices identified by the investigative committee.

Officials previously said six nationals of “Central Asian republics” had been detained on suspicion of recruiting for Isis and the former al-Qaeda affiliate Jabhat al-Nusra.

Isis supporters celebrated Monday’s attack but there has been no formal claim of responsibility from the group or any others.