People attend a religious service commemorating victims of a Russian airliner which crashed in Egypt, at St. Isaac's Cathedral in St. Petersburg, Russia, Nov. 8, 2015. Reuters/Peter Kovalev

As Russia continued to evacuate its citizens from the Egyptian resort area of Sharm el-Sheikh Monday, evidence grew that Metrojet Flight 9268 was likely brought down by a bomb in a terrorist attack killing all 224 passengers on board. The Kremlin may redouble its efforts to fight terrorism at home, especially in the North Caucasus region that has seen past terror attacks, as fears mount of potential domestic attacks, Bloomberg reported.

“We need to ring the alarm bells, there’s a significant increase in the level of risk,” said Rizvan Kurbanov, a parliament member for Dagestan. “If the problem was a local one in the past, now it’s in a number of other regions of the country.”

Terrorists linked with the group the Islamic State group, also known as ISIS, claimed responsibility for the Oct. 31 downing of the Metrojet flight, citing Russia’s airstrikes in Syria. Russia began airstrikes over Syria at the end of September saying they were aimed at fighting ISIS, however Western officials have questioned the Kremlin’s aims, saying some airstrikes have targeted opposition groups fighting Syrian President Bashar Assad.

ISIS Foreign Recruits | InsideGov

Only a few days before the downing of the Metrojet, Russian authorities had detained over 150 migrants over fears that they had ties to terrorists groups.

“A total of 1,756 persons are held in custody in the penal system for terrorist and extremist crimes, including 546 in pre-trial detention facilities, the rest in prison,” Valery Boyarintsev, deputy director of the Russian federal penitentiary service, said at the end of October.

People financing international terrorism have been found in 77 out of 85 of Russia’s regions, according to the Federal Security Service. Russia has claimed that over 5,000 Russians and people from other former Soviet states have joined ISIS. Russian President Vladimir Putin came to power amid domestic terror attacks and has continued to fight terrorism during his terms in office.