Security has been beefed up in Moscow Metro and major airports after an explosion that occurred around 2.45 p.m. local time.
The explosion hit a busy underground station in St. Petersburg, Russia killing at least 10 people and injuring dozens of others.
An official of Russia’s National Anti-Terrorist Committee said the explosion rocked a train travelling between Sennaya Ploshchad and Tekhnologichesky Institute stations.
Another explosive device was found and detonated at nearby Ploshchad Vosstaniya station.
Anti-Terrorism officials said it was too early to determine whether the blast was carried out by terrorists but Russian leader, Vladimir Putin said all possible causes are being investigated.
Mr. Putin who was in the city for a meeting with the President of Belarus, Alexander Lukashenko, said the government will do everything to take care of the injured.
No organisation has claimed responsibility for the blast yet.
Local media said the bomb, a home-made device filled with shrapnel, went off in the third car just after the train entered the tunnel.
The government told residents to be vigilant and announced that all surface transportation will be free until further notice. However, the city’s entire underground system was shut down after the attack.
“I appeal to you, citizens of St. Petersburg and guest of our city, to be alert, attentive and cautious, and to behave in a responsible manner in light of events,” said Georgi Poltavchenko, the governor of St. Petersburg.
The last fatal attack on an underground station in Russia occurred seven years ago when two explosions rocked stations in Moscow killing at least 33 people.
The suicide attacks were blamed on Islamic insurgent groups in Chechnya.
Terrorist attacks in Russia are mostly carried out by Islamic insurgents who fled Russia’s Northern Caucasus to join the Islamic State in Syria.
Russia deployed its military personnel in Syria in September 2015.