The Kremlin recognised for the first time on Tuesday that a bomb brought down a Russian passenger plane last month over the Sinai Peninsula in Egypt, killing all 224 people on board.Until now, Russia has played down assertions from Western countries that the crash was a terrorist incident, saying that it was important to let the official investigation run its course.Moscow says traces of foreign-made explosives were found on fragments of the downed plane and on passengers’ personal belongings. It believes a homemade device caused the airliner to break up in mid-air.With a 50 million dollar reward announced for information leading to the arrest of those responsible, President Vladimir Putin said:“This is not the first tine that Russia has faced barbarous terrorist crimes.“We won’t wipe the tears from our hearts and souls. This will remain with us forever. But that won’t stop us from finding and punishing the perpetrators.”Russian plane was brought down by a homemade explosive device, says official https://t.co/E2FbSa7X24 — TIME.com (@TIME) November 17, 2015Ordering Russia’s secret service to hunt down those responsible, Putin said the incident was one of the bloodiest acts in modern Russian history.“We will search for them everywhere wherever they are hiding. We will find them anywhere on the planet and punish them,” Putin said.Moscow pledged that part of its response would be more air strikes against Islamist militants in Syria.“It (our campaign) must be intensified in such a way that the criminals understand that retribution is inevitable,” said Putin.ISIL said it brought down the St Petersburg-bound plane, carrying mainly Russian tourists heading home from holidays in Sharm al-Sheik.According to security officials, two employees of Sharm al-Sheik airport have been detainedby Egyptian authorities in connection with the downing of the plane.“Seventeen people are being held, two of them are suspected of helping whoever planted the bomb on the plane at Sharm al-Sheikh airport,” one of the officials said.Egypt has not yet confirmed that a bomb was responsible, saying it wants to wait until all investigations are complete.