AKIPRESS.COM - The so-called Islamic State (IS) militant group says it was behind Wednesday's bombing of a supermarket in the Russian city of St Petersburg that injured at least 13 people, BBC reported.

IS made the claim on its Amaq news outlet but gave no evidence.

President Vladimir Putin had earlier described the blast at the Perekrestok branch as a terrorist act.

It came as he signed a new law on Friday toughening sentences for terrorist recruitment.

IS has recruited thousands of fighters from Russia and former Soviet states and President Putin has previously warned of the dangers they pose if they return home.

Russia's intervention in the Syrian war on the side of the government is believed to have made it a key target for IS and other militant groups.

Initial reports after Wednesday's blast suggested that it was being treated by authorities as attempted murder.

But Mr Putin, speaking at a military awards ceremony on Thursday, told the audience: "You know that yesterday in St Petersburg a terrorist act was carried out."

Russian officials described the bomb as a home-made device packed with lethal components that produced a blast equivalent to 200g (7oz) of TNT.