Russian President Vladimir Putin has ordered a full investigation into a blast on the St Petersburg metro line which killed at least 10 people early Monday afternoon.

The National Antiterrorism Committee said a bomb through the third passenger car as the train traveled between two stations – the Sennaya Ploshchad and Tekhnologichesky Institute stations.

Authorities labelled the bombing a terrorist attack.

The entire metro transit system was immediately shut down as bomb squads moved in to search for other possible explosive devices.

A security source said that another bomb had been found at a nearby metro station but offered no further details.

Some 20 people were also injured in the blast. Early investigations revealed that the bomb was homemade and filled with shrapnel.

“The causes of this event have not been determined yet, so it’s too early to talk about them. The investigation will show. Certainly, we will consider all possibilities: common, criminal, but first of all of a terrorist nature,” Putin said.

The BRICS Post with inputs from Agencies