TEN people were killed and about 40 injured when an explosion tore through a subway train in St Petersburg as President Vladimir Putin visited the Russian city yesterday.

Hours after the blast, police found another unexploded device in one of St Petersburg’s busiest subway stations, sending a wave of fear through Putin’s home city.

There was no immediate claim of responsibility for the attack, but Russian trains and planes have been targeted repeatedly by Islamic militants, mostly connected to the insurgency in Chechnya and other Caucasus republics.

The last confirmed attack was in October 2015 when Daesh militants downed a Russian airliner en route from the Egyptian resort of Sharm el-Sheikh, killing all 224 people on board.

The crash of a Russian plane carrying Red Army choir members near the southern city of Sochi on Christmas Day last year, in which 92 people died, is widely believed to have been due to a bomb, but no official cause has been stated.

Yesterday’s explosion came as a subway train travelled between stations at about 2.20pm local time.

The driver chose to continue on to the next station, Tekhnologichesky Institut, a decision praised by Russia’s investigative committee as aiding evacuation efforts and reducing the danger that passengers would die by trying to walk along the subway’s electrified tracks.

The train had been travelling from Sennaya Ploshchad station, heading south on the blue, north-south metro line.

After a few hours of differing casualty tolls, health minister Veronika Skvortsova said 10 people had died from the blast. City health authorities said 43 others were taken to hospital.

Witnesses said the explosion spread panic among passengers, who ran towards the exits of the station, which is 40 metres (130ft) underground.

“Everything was covered in smoke, there were a lot of firefighters,” Maria Smirnova, a student on a train travelling behind the one that was bombed, told the Dozhd television channel.

“Firefighters shouted at us to run for the exit and everyone ran. Everyone was panicking.”

The entire St Petersburg subway system, which serves some two million passengers a day, was shut down and evacuated.

Russia’s National Anti-Terrorist Committee said security was immediately tightened at all of the country’s key transportation sites. Moscow officials said this included the subway in the Russian capital.

Putin, speaking on television from Constantine Palace in the city, said investigators were looking into whether the explosion on the train was a terror attack or if it had some other cause.

He offered his condolences to the families of those killed.

Within two hours of the blast, Russian authorities had found and deactivated another bomb at another subway station, Vosstaniya Square, the anti-terror agency said.

It is a major transfer point for passengers on two lines and is the station from which most trains to Moscow depart.

Russian law enforcement agencies confirmed the Vosstaniya Square device was rigged with shrapnel and the Interfax news agency said it contained up to 1kg (2.2lbs) of explosives.

Social media users posted photographs and video from the Technology Institute subway station showing injured people lying on the floor outside a train with a mangled door. Frantic commuters were reaching through doors and windows, trying to establish whether anyone was inside.

St Petersburg, Russia’s second-largest city with more than five million residents, is the country’s most popular tourist destination but there was no immediate information on whether any foreigners were among the victims.

Nataliya Maksimova, who was running late for a dental appointment, entered the subway near the explosion site shortly after the blast. “If I hadn’t been running late, I could have been there,”

she said.

Putin was in St Petersburg to meet with Belarusian President Alexander Lukashenko, and went ahead with the talks after his television appearance to speak about the incident.

“Law enforcement agencies and intelligence services are doing their best to establish the cause and give a full picture of what happened,” Putin said.

Russian transport facilities have previously been the target of terror attacks.

Suicide bombings in the Moscow subway on March 29, 2010, killed 40 people and wounded more than 100 others.

Chechen rebel leader Doku Umarov claimed responsibility for the attack by two female suicide bombers, warning Russian leaders that “the war is coming to their cities”.

On November 27, 2009, in an attack that left 26 people dead and some 100 injured, a Moscow-to-St Petersburg train was bombed. Umarov’s group said he also ordered this attack.

Russian airports have also been targeted. On January 24, 2011, a suicide bomber blew himself up at Moscow’s Domodedovo Airport, killing 37 people and wounding 180.

At the same airport in August 2004 Islamic suicide bombers boarded two planes and brought them down, killing a total of 90 people.

US President Donald Trump called yesterday’s explosion an “absolutely a terrible thing”.

Trump spoke before a working lunch with Egypt’s President Abdel-Fattah el-Sissi. He said of the attack: “It’s happening all over the world”.