At least 10 people have been killed and some 50 injured in an explosion on a train in the subway system of the Russian city of St. Petersburg. All stations were closed after the blast.

An explosion in a train carriage on the St. Petersburg subway system on Monday killed at least 10 people and injured some 50 others, Russian authorities said.

The blast was reported to have taken place in a train traveling between the stations of Sennaya Ploshchad and the Institute of Technology. A spokesman for Russia’s National Anti-Terrorism committee (NAK), Andrei Przhezdomsky, said in televised remarks that the blast occurred at 2:40 pm local time (1140 UTC).

St Petersburg metro blast: Timeline

Interfax news agency quoted an unnamed source as saying the explosion was caused by a shrapnel-filled bomb. The blast tore a hole in the side of a carriage.

The NAK later said it had found and deactivated another homemade bomb found at a different St. Petersburg station.

Terrorism ‘being considered’

Following the explosion, there were scenes of confusion, with traffic blocked on the busy thoroughfare of Moskovsky Prospect, while emergency vehicles and a helicopter rushed to assist the victims.

All stations on the subway system were closed following the blast. The Moscow metro also said it was stepping up security in case of an attack there, while the Russian National Anti-Terrorism Committee said security would be tightened at all criticial transport facilities.

President Vladimir Putin, who was visiting the city for talks with his Belarus counterpart, Alexander Lukashenko, expressed his condolences to the families of those killed in the blast, and said all possible causes, including terrorism, were being considered.

“Law enforcement agencies and intelligence services are doingtheir best to establish the cause and give a full picture of what happened,” Putin said at the start of his talks with Lukashenko.

German Foreign Minister Sigmar Gabriel expressed his condolences following the blast, saying he had learned of the news “with deep sorrow.” He said Germany’s thoughts were “with our friends in Russia, the victims and their families in this dark hour.”

Several enemies

Russia has seen several attacks by separatist Islamist Chechen militants in past years, and the extremist group “Islamic State” (IS) has also threatened to carry out attacks in the country in retaliation for the Russian military operations in Syria. Russia is giving military assistance to Syrian President Bashar al-Assad in fighting rebel groups including IS.

There has, however, been no immediate claim of responsibility for the blast.

Double suicide bombings in the Moscow subway in March 2010 killed 40 people and wounded more than 100 others. Those attacks, carried out by two female suicide bombers, were claimed by Chechen rebel leader Doku Umarov.

In November 2009, 26 people were killed and some 100 injured in a bombing on the high-speed Moscow-to-St. Petersburg train, with Umarov’s group saying he also ordered that attack.

tj/rc (Reuters, dpa, AP, AFP)