Russia's chief intelligence officer confirmed Tuesday that last month's Metrojet plane crash was the result of a terrorist attack, as widely speculated.

Reuters reports President Vladimir Putin vowed to take action against those responsible, ramping up airstrikes against Islamic State militants in Syria.

"We will find them anywhere on the planet and punish them," Putin said during a Kremlin broadcast Tuesday.

Metrojet Flight 9268 was headed from the Egyptian resort Sharm el-Sheikh to St. Petersburg on Saturday, Oct. 31, when the Airbus A321-200 exploded in midair shortly after take off, crashing in the Sinai Peninsula. All 224 people onboard were killed.

Despite the Egyptian government's protests to the contrary, U.S. and U.K. analysts determined the crash was likely due to an explosive smuggled onboard the plane. Britain and other nations halted flights to Sinai and evacuated tourists from the area.

Until now, Russia downplayed Western theories of a terrorist attack, calling for the investigation to run its course.

The recent attacks in Paris may have motivated this change in rhetoric. Alexander Bortnikov, the head of the FSB, held a late night meeting in which he confirmed traces of foreign-made explosives were found at the crash site.

"According to an analysis by our specialists, a homemade bomb containing up to 1 kilogram of TNT detonated during the flight, causing the plane to break up in mid air, which explains why parts of the fuselage were spread over such a large distance," Bortnikov said. "We can unequivocally say it was a terrorist act."

Although Egypt still has not confirmed a bomb caused the crash, Egyptian authorities have apprehended several suspects in connection with a possible attack, including two airport employees.

"Seventeen people are being held, two of them are suspected of helping whoever planted the bomb on the plane at Sharm al-Sheikh airport," an anonymous security official said.

Putin said Russia would strengthen attacks against ISIS militants.

"Our air force's military work in Syria must not simply be continued," he said. "It must be intensified in such a way that the criminals understand that retribution is inevitable."

According to The New York Times, Russia has already begun to fulfill that promise. A Russian submarine fired advanced Kalibr cruise missiles from the Mediterrenean at ISIS targets in Raqqa, Syria. Social media accounts from the Russian defense ministry also show Russian aircraft, including Tupolev Tu-95, Tu-22 and Tu-160 strategic bombers, lunching strikes against positions in Syria.

The Russian news agency TASS reports Putin called for the Russian military to cooperate with France in the campaign against ISIS.

"A French aircraft carrier task force is to approach your area soon. You are to establish direct contact with the French counterparts and cooperate with them as with allies," Putin said.