Russia‘s President Vladimir Putin speaks during a meeting with the State Council Presidium on developing the fisheries sector at the Novo-Ogaryovo state residence outside Moscow, Russia, October 19, 2015.

President Vladimir Putin said on Tuesday Russia had foiled 20 militant attacks this year and was stepping up efforts to root out domestic terrorism, almost three weeks after launching air strikes against Islamist fighters in Syria.

The Russian authorities have arrested a number of suspected militants since the Syria campaign started on Sept. 30, a development that stoked fears that militants could seek revenge by attacking targets inside Russia.

A week ago, Russia’s FSB Federal Security Service said it had foiled a plot to attack Moscow’s busy underground using explosives, news that rekindled painful memories among Russians of a series of deadly attacks on the metro in the 2000s.

Some of the men arrested in connection with the plot had undergone Islamic State of Iraq and Syria (ISIS) training in Syria, the FSB said.

Speaking at a meeting in the Kremlin with military officers, Putin said the FSB had killed 112 militants and arrested more than 560 so far this year.

“The complex international situation demands that we strengthen our counter-terrorism work including inside our own country,” said Putin.

“We need to act just as energetically and efficiently (as in the past). It is vital to expose the links between Russian militants with international terrorist groups and their sponsors.”

Putin spoke as police said they had detained 20 suspects they accused of financing terrorism and advocating the creation of an Islamic caliphate on Russian soil.

The interior ministry said it had conducted a search of 24 addresses in the Moscow region where members of outlawed organisation Hizbut Tahrir resided.

“The members of the extremist organisation were recruiting new followers, distributing banned religious material and raising funds, including to help finance armed militants,” the ministry said in a statement.

Putin said ISIS militants in Syria were planning to destabilise other regions and were recruiting Russians and citizens of other former Soviet states with a view to expanding their operations.

“Having established a foothold in Syria and other Middle East countries, the terrorists have been building plans to increase expansion and destabilise entire regions,” RIA quoted Putin as telling high-ranking officers.

Russia’s main breeding ground for Islamist militants is in the mainly Muslim North Caucasus region, including in the internal republics of Chechnya, Dagestan and Ingushetia, where Islamist insurgencies have been simmering for years.

The Kremlin has fought two wars in Chechnya since the 1991 Soviet collapse and now relies on loyalist Chechen leader Ramzan Kadyrov to use force to keep relative peace in the region.

Russia says it is also worried about the possible spread of jihadism to the former Soviet republics of Central Asia, a region Russian strategists have traditionally called the country’s “soft underbelly.

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