Russian President Vladimir Putin pledged to step up air strikes in Syria after Moscow confirmed a bomb brought down a Russian passenger jet in Egypt last month

Russian President Vladimir Putin pledged to step up air strikes in Syria after Moscow confirmed a bomb brought down a Russian passenger jet in Egypt last month, the Kremlin said Tuesday.

The Russian plane crash in Sinai, Egypt, was caused by a terrorist attack as traces of explosives have been found in the wreckage of the plane, Federal Security Service director Aleksandr Bortnikov told President Vladimir Putin.

“We can say that that [Sinai plane crash] was a terror act,” Bortnikov told Putin. According to the FSB chief, experts analyzed passengers’ belongings as well as the parts of the plane. “After the examination on all these objects, we have found traces of a foreign-made explosive substance,” Bortnikov said.

“During the flight, a homemade device with the power of 1.5 kilograms of TNT was detonated. As a result, the plane fell apart in the air, which can be explained by the huge scattering of the fuselage parts of the plane,” he added.

This not the first time that Russia has faced “barbarous terrorist crimes, more often without apparent causes, outside or domestic, as it was with the explosion at the railway station in Volgograd at the end of 2013,” He added: “We haven’t forgotten anything or anyone. The murder of our nationals in Sinai is among the bloodiest crimes in [terms of] the number of casualties.”

President Putin has vowed to find and punish the culprits behind the Sinai plane attack. “Our military work in Syria must not only continue. It must be strengthened in such a way so that the terrorists will understand that retribution is inevitable,” he said.

The Federal Security Service director also announced a reward of $50 million for information on those behind the terror attack on the A321.

The Russian president asked the Foreign Ministry to “call on all our [foreign] partners” to assist in the search for the terrorists behind the attack. “We look forward in the course of this work to [help from] all our friends, including in finding and punishing the criminals," he added.

Russia will act in accordance with Article 51 of the UN Charter, which provides for countries’ right to self-defense, Putin said. “Those who attempt to assist criminals should be aware that the consequences of such attempts will be entirely their responsibility,” he added.

The Kogalymavia A321 air crash took place over the Sinai Peninsula in Egypt on October 31. All 224 people on board the plane were killed, making it the deadliest air accident in modern Russian aviation history.