Russian President Vladimir Putin has signed into law a bill increasing penalties for the recruitment of extremists, the latest measure to address what officials have described as a threat from militant fighters returning home from the Middle East.
Official publication of the law on December 29 came two days after 14 people were injured in a bomb attack on a supermarket in St. Petersburg that Putin called an "act of terror."
The Islamic State extremist group -- which Russia has targeted in Syria as part of its bombing campaign backing the government of Syrian President Bashar al-Assad since 2015 -- claimed responsibility for the attack on December 29.
Putin, who faces re-election in March, has stepped up warnings against extremists, declaring on December 28 that they face being "liquidated on the spot" in Russia.
The new law, approved by Russia's parliament earlier this month, stiffens the penalties for recruiting and financing extremists and disseminating "terrorist propaganda," including by raising the maximum sentence for recruitment and financing to life from 10 years.
Russian security officials have voiced concern about the possibility of extremist fighters returning home to Russia from the Middle East, where IS this year was ousted in a series of battles from most of the territory it once controlled in Iraq and Syria.
The FSB recently estimated that the number of Russian fighters who joined IS and other extremist groups in the Middle East, North Africa, and elsewhere numbers over 4,500.
Russia's FSB security service said two weeks ago it had broken up an IS cell planning a December 16 terror attack at an Orthodox cathedral which is a key tourist attraction in St. Petersburg.
Putin said afterwards that the attack was foiled with the help of the U.S. CIA.