Image source, EPA

As the evening draws on in St Petersburg, locals are paying tributes  to those killed and injured on Monday's attack.

The cause of the explosion has yet to be confirmed. Here is a round-up of what we know:    

• The explosion happened at about 14:30 local time (11:30 GMT) between Sennaya Ploshchad and Tekhnologichesky Institut stations

• Up to 10 people were killed with at least 37 injured, Russia's health minister says
• Another device was later found at a nearby station and made safe
• Passengers were  captured on video  escaping a smoke-filled platform    
• President Vladimir Putin said all causes, including terrorism, were being investigated
• No-one has said they were behind the blast but local media released CCTV footage of a bearded man
• Foreign leaders have condemned the incident, with US President Donald Trump describing it as a "terrible thing".

We are ending our rolling coverage on this live page but you can continue to follow the latest developments  via our news story  and here is everything we know about Monday's events.     

Russian President Vladimir Putin has thanked St Petersburg's drivers for taking people home while metro services are suspended.

He said many motorists and taxi drivers were offering to carry passengers for free. 

Hundreds of thousands of people in the city are travelling by foot, car, tram or bus while the metro system is closed, Mr Putin added.

Image source, AFP/Getty

US President Donald Trump kept his thoughts on events in St Petersburg brief during an event at the White House.

Image source, Reuters

We've been bringing you quick updates as new information comes out about the St Petersburg explosion, and have now compiled a round-up of what we know  here .

Pictures of the aftermath can be found here .

The US ambassador to the UN has said her country stands with Russia against "extremist groups", despite authorities keeping an open mind about the cause of the explosion.

Nikki Haley shared a message of support for the people of St Petersburg, after up to 10 were killed on Monday.

Russia's Investigative Committee, a state body which investigates major crimes, earlier said it was treating the explosion as a suspected "terrorist attack" - but was not ruling out other possibilities.

"Despite the fact that a criminal case under article 205 of the Criminal Code (act of terror) has been opened, the investigation intends on verifying all other possible versions of this incident," the committee said in a statement.

It has not pointed to possible perpetrators.

Senator Viktor Ozerov, who heads the Russian defence committee, said that anti-terror measures appeared to have failed on Monday.

"The tragedy in St Petersburg tells us that, somewhere, the anti-terror measures that have been taken... have not worked," Mr Ozerov said.

Speaking at the Russian parliament, he called for an investigation into the security measures in place on the St Petersburg metro system. 

"Now we need to uncover the reasons why our system failed, and work out a series of measures so as not to allow such mistakes to be repeated." 

His statement was broadcast live on the state-run news channel Rossiya 24.

Image source, Getty Images

A woman travelling in the carriage next to the blast has described the moment the explosion ripped through the train to local media.

The woman, named only as Polina, told Bumaga ( in Russian, external ) it was standing room only as the metro moved between Sennaya Ploshchad and Tekhnologichesky Institut.

When the train finally pulled into the station, she said they "saw that the neighbouring carriage was mangled, window glass was broken, there was no light and there was blood".  

Frank Gardner
BBC Security Correspondent

The metro driver made the right decision not to stop his train before reaching the station, Russia’s Investigative Committee has said.

In a statement released on their website, the federal investigating authority said his actions may have prevented further victims and allowed for the swift evacuation of the injured.

The blast took place in the tunnel between two stations in central St Petersburg.

Oliver Carroll, the managing editor of the Moscow Times newspaper, has been speaking to BBC World News television.

He said that people in St Petersburg are not used to dealing with such attacks.

There have been attacks in Moscow in recent years, but the last major one was in 2010. In fact, Russia's main cities have been "remarkably terror-free" in the last few years, he says.

Mr Carroll says the security services have been "fairly uncompromising" in the troubled North Caucasus region, which is mainly Muslim, as well as taking "bold action" in Syria.

"So there is the grounds for an Islamic kind of terrorism," he said. "At the same time, there will be various conspiracy theories about the state themselves being behind it."

He cautions, however, that he does not want to give "too much weight" to such theories.

What is without doubt is that the government's response "will be uncompromising".

BBC Monitoring

Russian Prime Minister Dmitry Medvedev has written on Facebook:

While Mr Medvedev calls it a terrorist attack, some Russian officials have been careful to not label it as such until their investigations are complete.

CCTV images of the man suspected to be responsible for the St Petersburg explosion are circulating on social media.

The images appear to show a bearded man wearing a hat.

Earlier the Interfax news agency reported that CCTV cameras had captured images of the suspect.

The BBC cannot confirm any of these reports, and Russian officials are still investigating the cause of the explosion. 

Russia has a history of attacks on public transport.

In 2013, two bomb blasts in two days in the south-western city of Volgograd left more than 30 people dead and 62 needing hospital treatment.

The suicide bombings struck at the railway station on 29 December and on a bus on 30 December.

Volgograd's public transport system had already been targeted earlier in 2013. In October, a female suicide bomber killed at least six people when she detonated the explosives on a bus.

Three years earlier, at least 38 people died in a double suicide bombing on the Moscow metro .

Before that, in 2009, a bomb exploded  on a high speed train  travelling between Moscow and St Petersburg, killing 27 and injuring another 130.

All attacks were claimed by Islamist groups.

• An explosion has hit a train between two underground stations in St Petersburg
• Officials say the cause of the blast, between Sennaya Ploshchad and Tekhnologichesky Institut stations, is yet to be determined 
• A spokesman for St Petersburg's governor says at least 10 people have been killed and 50 injured. But the Russian National Anti-Terrorist Committee says the death toll is nine, with 20 hurt
• The committee said an explosive device was later found and made safe at another station, Ploshchad Vosstaniya  
• President Vladimir Putin says all causes, including terrorism, are being investigated
• You can read our main story here
• And here is a gallery with pictures of the aftermath

This is reminiscent of the London and Paris attacks – the hashtag #домой, external (#Domoi) is a big thing now.

On VKontakte, a social media network popular among Russians, and now also Twitter.

It means ‘Home’ – and ordinary people are using it to help others get home.

Here are two examples from VKontakte:

"Around 6pm. We’re able to take three people to the coastal district. We’re going by the toll road. FREE. #Domoi."

"Guys! I have to get home to Muzhestva Ploshchad. Can anyone get me at least some of the way? #Domoi." 

Rick Macy, 52, from Massachusetts, works in St Petersburg and was in a metro car three stops away. He heard the driver and dispatcher talking about the incident and he got off the train.

BBC Monitoring
News from around the globe

Russia's National Anti-Terrorist Committee says a home-made explosive device has been disabled at Ploshchad Vosstaniya metro station in central St Petersburg.

It said an "improvised explosive device has been discovered and disabled in a timely manner”.

The station is located about two miles away from the Tekhnologichesky Institut station.